It's fair to say that when Warner Bros announced that McG would be directing the latest Terminator movie, the reaction they got was something of a shock. Only the words "Brett Ratner", hated despoiler of X-Men, could have provoked more vocal fanboy consternation. But if the studio reeled slightly, McG himself wasn't all that surprised. People have been judging him before they've even met him since he was a kid.

"It's partly the name," says McG, relaxing on a sofa in the offices of his production company Wonderland Sound & Vision.

"I mean what kind of asshole goes around calling himself McG? It's real fun to hate that guy." Well it might partly be the name (not, as most people assume, a piece of faux hip-hoppery but a long-standing nickname given to him by his parents when he was a child as a result of there being three Joe Nichols in the house: his middle name is McGinty which became McG). But it also might be something to do with the films. An ex-music video director who made his name with promos for Korn and Sugar Ray before moving on to high-profile commercials for Coke and Gap, his contribution to cinema runs to Charlie's Angels (2000), Charlie's Angels: Full Throttle (2003) and We Are Marshall (2006), a slightly soapy true tale of a sports tragedy whose only real surprise was Matthew McConaughey declining to remove his shirt. None of it immediately suggests he's the right guy to take the reins of James Cameron's time-warping cyborg epic.

"Oh yeah, I was completely aware of the fact that the reaction was 'fuck this Charlie's Angels guy!'" he declares, "but I'm willing to let the work do the talking. I'm tired of being the cheerleader for my films. I'm no stranger to being the long shot. My whole life has been from a place of disadvantage. I've got to the point where I don't give a fuck."

Terminator Salvation got a slug of unwanted publicity when the now infamous Christian Bale flame-out hit the internet. McG declines to comment any further than he already has, but points out that movie sound stages can be stressful places where creative battles sometimes become heated. Particularly, it seems, on his sound-stages. "I'm reintroducing the fist-fight to movie sets," he smiles. "I don't think there's been a film I've made where there hasn't been some kind of physical fight. I mean, I've been headbutted by an A-list star. Square in the head. An inch later and my nose would have been obliterated." Will he be revealing any names? "Nah, I probably shouldn't," he smiles. "But it was Bill Murray. Y'know, it's a passionate industry."

Complicating McG's life even further is what he describes as a "long-standing broad spectrum anxiety disorder". This is no trivial slice of SoCal psychobabble. It's a real condition and it's cost him dearly, at one point threatening to completely derail his career. In 2004, after a couple of years of on-again-off-again preparation, he was set to direct JJ Abrams's screenplay of Superman: Flyby, scheduled to be shot in Australia, only to find himself, at the last moment, in the throes of an epic anxiety attack and unable to board the Warner jet, which was pretty much idling on the runway.

"I learned a lot about myself in that moment," he says ruefully. "It really was the lowest point in my professional life and utterly embarrassing. I've got it under control now but I'm like the fat guy who loses 200 pounds. He knows if he loses focus he'll return to who he was in a heartbeat." It must go towards calming his nerves that Terminator Salvation is as certain a box office hit as they come. Is he relishing the thought of proving a lifetime's worth of naysayers wrong?

"Nah, I don't think that way. I've been kind of humbled enough by my own neuroses along the way. I've experienced too much humiliation and depression and sadness to grab my cock and begin slapping people in the head with it. I have a great deal of empathy for what people go through. My brother died last year of a drug overdose, which was the shittiest thing that ever happened to me. People always get the wrong idea about me. There's this idea that I'm this sunny guy living in California making little pop videos and fucking beautiful women - my life isn't like that."

Not for the first time, it seems, everyone is wrong about McG.

• Terminator Salvation is out on Fri