It has always been an irritating paradox that Adrien Broner is so classy with gloves on and wilfully obnoxious anywhere near a microphone.

Both sides of the Cincinnati Loudmouth, a former four-weight world champion, were seen when he toughed out a majority draw over 12 rounds at 144lbs catchweight against Jessie Vargas in Brooklyn on Saturday night. He shook hands with his opponent in the ring and smiled briefly, then, after brushing aside the Showtime interviewer, Jim Gray, unleashed a slew of racist and homophobic insults that shocked all but his own hardcore team and supporters.

“I beat your ass,” Broner told his opponent. “You need to settle down,” Vargas replied. So far, so familiar.

Then, confusing Martin Luther King with Rodney King – the black victim of an horrific attack by Los Angeles Police in 1991 – Broner said of Vargas: “I beat him like I was using what they used to beat Martin Luther King.”

When Vargas remarked, “We went at it for 12 rounds‚“ Broner replied, “We didn’t go at it. That’s gay. Going at it is gay.”

He was not finished: “But let’s go to my town. I want to fight him where I’m from. There’s hella Mexicans that are in here, they kept booing me and shit. They want rice and chicken. I want some motherfuckers that want Coney’s [hot dogs] around me.”

But here is the other paradox. Broner sells. It was his usual lack of respect in the build-up that helped to fill the Barclays Center to near its 19,000 capacity – something the WBC heavyweight champion Deontay Wilder could not manage against Luis Ortiz last month.

This was a close, untidy fight that was tough to call. “How do you score a fight?” Darren Barker asked on Sky. “Sometimes I’ve liked Broner, sometimes I’ve liked Vargas.” The former world middleweight champion scored it a draw, as did the two judges who saw it 114-114, the third giving it to Broner 115-113. The Guardian had Broner up by a round.

Between 2011 and 2016 Broner held world titles at super-featherweight, lightweight, light-welter and welter. Six years ago the Ring magazine ranked him No 5 pound for pound in the world. And along the way he has gathered as many ring nicknames as his one-time mentor, Floyd Mayweather Jr: Lil Brother, AB (About Billions) and, pointedly, The Problem. He has created plenty of problems, in and out of the ring.

Earlier on Saturday night in Belfast BoxNation showed the way more acceptable face of boxing. It could hardly have been a greater contrast. After losing a quality 12-rounder to Carl Frampton in front of his Irish fans, the Filipino Flash, Nonito Donaire, bumped into the winner in the corridor and exchanged the sort of pleasantries Broner would probably scoff at.

Beforehand Frampton said of the former world champion, “He’s a future Hall of Famer. Hopefully I can put myself in that bracket one day. He is the best fighter that I will have ever fought. That includes Leo Santa Cruz and [Scott] Quigg and everyone else.”

The margins on the cards in this one were wider – all 117-111 – and the loser had no problem with that. Before leaving the building, he told Frampton, “Whatever you need that I can help with … Belfast has been amazing to me. You’ve been amazing too. I had so much fun in the fight. You did well. You’re smart.”

“Appreciate it, man,” Frampton said, as they hugged and said goodbye.

Boxing, more than nearly all sports, demands contrived aggression between strangers. And the business side of the fight game is driven by manufactured malice and noise. Broner, who has had his problems away from the ring and has an explosive nature, would seem to be temperamentally suited to gratuitous trash talk. Vargas appeared to laugh it all off later, so he was not hugely offended; then again, he will be angling for a lucrative rematch.

Frampton and Donaire, meanwhile, boxed and resolved their dispute over a mere bauble – the WBO’s interim featherweight belt – as well as a fair amount of cash, like gentlemen. It is an old-fashioned concept but not out-dated. It should be the norm but it never will be.