Last week, when on the red carpet for his new film Sicario: Day of the Soldado, Benicio Del Toro was asked about the Trump administration’s decision to remove the children of undocumented migrants from their parents. “What’s the morality inside this monster for separating children from their parents?” he asked of Trump, adding that it was “immoral” and he was “horrified”. In fact, the Sicario sequel has become an unlikely lightning rod for one of the biggest political stories of the year.

A week later, Puerto Rico-born Del Toro, 51, is still in combative mood and urging restraint from the US government (which has said it will stop the separations) and a common-sense solution. “It’s amazing that I’m in the middle of talking to the press about this movie and it happens that the biggest story in the world right now is what the government is doing to these families.

“Being very honest, we have to start with the premise that they broke the law,” he says. “But innocent until proven guilty. They’ve been ‘guiltied’. They separated the families as if they’re criminals. Wait; keep them together and investigate. Some of those people deserved to have a second chance to start their lives in a new setting like the United States.

“They’re running from really bad circumstances, they’re in despair, they’re hoping for a better life. That’s separate from Sicario,” he says, cautiously. But the film does focus on the importance of that border both politically and in terms of the cartels. Is it that much of a leap? “You can spin anything in any direction. I don’t think Sicario is saying anything.”

Del Toro’s filmography says a lot about one specific subject: the drug war. His relationship with the genre goes way back. His really big break came in 1989 with License to Kill, Timothy Dalton’s second and final Bond film where, as a 21-year-old, Del Toro played a cartel henchman who ends up getting crushed under an industrial-sized cocaine grinder. Subtle, it wasn’t. He was paid $40,000 for the role, and then couldn’t find work for a year, so he watched Fellini and Kurosawa films instead. When he reemerged in the 90s, he built a career in which he “played every angle on the drugs”. He was the guy who sells the drugs (Escobar: Paradise Lost), the guy who steals the drugs (Usual Suspects), the guy who takes the drugs (Fear and Loathing in Las Vegas), the cop who tries to stop the drugs (Traffic), the cartel enforcer (Savages) and the guy who hunts the cartel enforcers (Sicario).

“It’s become a genre. You can see it,” says Del Toro. “Maybe Easy Rider was one of the first movies to deal with it in a way, but more so the French Connection and [Brian De Palma’s] Scarface. They’re becoming the new westerns.”

“Think about it,” he adds. “That Bond movie had something to do with the genre we’re talking about. James Bond is fighting with the cartel and that’s in 1989. It’s been going on for a long time.”

Of all of his drug war films, Sicario might be the best. In 2015, 25 years after Dalton single-handedly fought off a cartel with little more than a stiff upper lip, Denis Villeneuve’s film managed to reinvent the narco thriller. Where the likes of Netflix’s Narcos focused on the personalities that drove the violence, Sicario lifted the curtain on the lengths the US government will go to in a seemingly unwinnable war, and what happens when someone with a moral code gets mixed up in it.

Emily Blunt was the fledgling FBI agent who ends up out of her depth and compromised. Del Toro’s Alejandro Gillick was the former cartel lawyer turned CIA asset and assassin out for revenge, while Josh Brolin was his duplicitous, ruthless handler. From its grisly opening scene of a cartel massacre, to its big set pieces on either side of the Mexican border, it was a potent mix of ultra violence, double crosses and storylines ripped from the headlines.

But when the sequel, Sicario: Day of the Soldado, was announced without Blunt or Villeneuve attached, fans and critics worried it wouldn’t live up to the original. So did Del Toro. “The first one was tight and it did its own thing very well, in my opinion,” he says. “So I was a little apprehensive [about the sequel], and then, when I heard that Denis wasn’t able to do it, that was a little bit of a red flag.” Gomorrah director Stefano Sollima was brought in to direct, and the script follows a similar pattern and pace to the original – which was also written by Taylor Sheridan. But the conversation around the film isn’t about on-screen violence, nihilistic machismo or the cartels – but immigration at the US and Mexico border.

In the past, Del Toro has said that he is not “too political”; has being thrust into the conversation about US immigration changed his stance?

“Have you seen my career?” he asks. “Have you seen what I do? Come on. Sometimes you say things and they can be put out of context. I am political, and I’m not. I’m a human being. If they got a guy on the moon, someone has got to be able to organise this.”

There is more than a hint that Del Toro isn’t particularly comfortable being a spokesman on the issue of child separation (he has a six-year-old daughter, Delilah, with Kimberley Stewart). During his career, he has mostly let his work do the talking, only rarely lifting his head above the parapet, such as when he said he was in favour of legalising marijuana. “Whisky is just like rum; you drink a lot of it you’re going to get a hangover,” he says. “Drugs are more complicated. Marijuana is not like heroin. Marijuana is not like meth, so it gets a little bit more complicated.”

‘I’ve had people talk to me about Sicario as if it’s a documentary,’ says Del Toro. Photograph: Barry King/WireImage

A recent profile described him as “the James Cagney of the drugs war movie”, but in person Del Toro has similarities with his more out-there characters, such as Fenster, the mumbling hood in Usual Suspects, or the zombified cop Jack Rafferty in Sin City.

He is a tall man (he was once a promising basketball player), but not imposing. He wears a suit and tie, which he seems to be fighting to get out of. In the past, Del Toro has admitted to wanting to be in the same club as Sean Penn, Gary Oldman and Mickey Rourke: tough, masculine actors you go to see regardless of what films they are in. “I still look up to those guys,” he admits, but won’t say whether he feels he is in their class. “I don’t know, I think someone else needs to define that.” In truth, he’s cooler than all of them – without half their baggage. If being an Oldman fan is like following Manchester United, being a fan of Del Toro is the equivalent of supporting Hamburg’s St Pauli – the footballing outsiders with a skull and crossbones on their flag.

His trademark laconic drawl only adds to his appeal, even if his points are sometimes hard to grasp. When I ask him about Alejandro’s journey from killer to saviour in Sicario, he goes off on a contradictory tangent worthy of Fenster. “Just because you start acting right it doesn’t mean I’m going to forget about your past,” he says, picking up a metaphorical gavel. “I’m not going to forgive him, but I might spare his life or maybe I reduce his sentence, but he’s still going to have to do time. If I was going to judge him … I don’t judge my characters. Well, I do, but I don’t. I mean, I’m judging him now because I can do whatever the hell I want … I try to understand him.”

With Johnny Depp in Fear and Loathing in Las Vegas. Photograph: Allstar/MCA/Universal

Get Del Toro on a subject that annoys him, however, and he snaps into focus. For example, he is less than impressed with how some journalists have interpreted the second Sicario movie. “I’ve had people talk to me about Sicario as if it’s a documentary,” he says. “Someone just said to me: ‘Your movie has to do with the exact same thing that’s going on right now [on the border]. You take a child and you separate her from her father.’ I go: ‘What?’ He says: ‘You separate the girl from the family.’ I say: ‘No, no, I kidnap the girl. It’s very different.’”

Del Toro has had a similar problem before. After he starred in the adaptation of Hunter S Thompson’s Fear and Loathing in Las Vegas, as Oscar Zeta Acosta, AKA Dr Gonzo – the journalist’s frazzled lawyer – he gained an unwelcome reputation. He put on weight for the role by eating a diet of 16 doughnuts a day for two months. “I gained weight stupidly in eight weeks,” he remembers. “I didn’t get a trainer. I did it macho style, stupid style. I gained the weight really quick and it took a while to take it off.

“So, during that time, in between work, I had meetings and people saw me and said: ‘Oh my God, this guy went off the rails.’ They hadn’t seen the movie; they don’t know what I’m doing. I could be walking to a 7-Eleven and some producer could be there saying: ‘Was that Benicio Del Toro? I saw him last week – what happened to him?’”

He says a cocktail of “gossip and bullshit” led many in the industry to believe he was an unsafe bet who had a drink and drug problem. “People in Hollywood can be as gullible as anywhere,’ he says. “Just because they’re in the world of make-believe, it doesn’t mean they don’t believe it. The fact is that, after I tried to get a couple of jobs, the feedback I got was that people didn’t want to see me because ‘We know he’s got a drink problem, and we know he’s got a drug problem’. And the only reason for that was because they had seen Fear and Loathing. Maybe it was a compliment.”

Del Toro won best actor at Cannes for his portrayal of Che Guevara. Photograph: Laura Magruder

But Del Toro reversed this tide. In 2001, he won a best supporting actor Oscar for his role as the principled Mexican cop Javier Rodriguez in Steven Soderbergh’s drug war epic Traffic, and, seven years later, won best actor at Cannes for his two-part portrayal of the life of Che Guevara. He got a reputation as someone who could take seemingly obvious narco characters and give them new depth. It has been a deliberate choice – and one informed by Denzel Washington. “Denzel is one of those actors who has had to deal with all those stereotypes,” Del Toro says. “It’s an interesting journey. Me being Latino, I’ve looked at his career [to] see how to navigate and take those stereotypes and flip them upside down.”

In the past, Del Toro has alluded to the typecasting he has fought to subvert throughout his career. In 2004, he said he would “rather play the guy who is driving in a convertible with sunglasses and gets the girl at the end”. At the beginning of his career, someone tried to change his name to Benny Dell, “because it wasn’t Smith, or Anglo, or whatever”. Would he still like to try a romantic comedy? “I wouldn’t mind doing something light, but that’s going to be work,” he says. “Those roles don’t come to me first usually, but [the films] about guys who are conflicted with things exploding come to me. Why is that? You could say typecasting or because of the shape of my eyes. You could say many things. I don’t care. Good stuff is good stuff, I don’t care if it’s upside down or inside out.”

As the interview comes to an end, Del Toro asks me about the T-shirt I am wearing. I tell him where it’s from and then he says: “Let me ask you something. When you put that on, did you know that you were putting that on?” Yes, I say, not really understanding where this is going. “Because when Melania Trump got on that plane,” he says, referring to her “I REALLY DON’T CARE, DO U?” jacket, “she knew what she was putting on.”

Behind all the stumbling and the flipflopping, Benicio Del Toro knows exactly what he’s doing, too.

Sicario: Day of the Soldado is released in the UK on 29 June.