James Corrigan: Merchant of menace proves a good old'un will always win the argument on points

The Way I See It: Merchant remembers all the promises, all the claims to immortality, all the baloney – and, when required, he throws it back at them, in a blast of reality

A clash of the generations is always guaranteed a chorus of laughter in the slophouse. The old man still believes he's got it and so challenges the young bruiser doling out the impertinence. "I wish I was 50 years younger, I would kick your ass," he says, as the cheeky upstart is led away in bemusement and not a little embarrassment.

But this wasn't the Dog and Duck in Leytonstone and this wasn't some OAP so proud to have completed his National Service and who claimed to have known the Krays. This was Home Box Office and this was the analyst Larry Merchant. Furthermore, the young bruiser the 80-year-old was squaring up to just happened to be Floyd Mayweather, aka one of the two best fighters in the world.

Fortunately, YouTube, the modern sports fan's greatest aid, is on hand to replay the showdown. On Saturday night, Mayweather knocked out Victor Ortiz when his opponent wasn't looking. Ortiz, the 24-year-old welterweight champion, had just been deducted a point for an intentional butt and was still trying to apologise when Mayweather pounced. Not only were Ortiz's gloves down but his gaze was directed towards the referee. First came the left and then the right followed – lights out. It was legal, but was it sporting? Think India and that run-out of Ian Bell.

But this isn't cricket, this is boxing. And when the head hits the canvas and the number 10 is called there's no way back. So Mayweather raised his arm, the crowd booed and Merchant strode into the ring. Mayweather knew what awaited. Indeed, Merchant was barely through the inevitable "was that the right way for a champion to win?" question when Mayweather acted on the impulse that the best course of defence is attack. HBO has long wanted him to fight Manny Pacquiao and tensions are at tipping point. Very conveniently, Merchant was in the firing line.

"You never give me a fair shake," screamed Mayweather, going eyeball to eyeball as he would at a weigh-in. "HBO need to fire you. You don't know shit about boxing. You ain't shit." "What you talking about?" replied Merchant, himself stepping forward. And, as the corner men dived in, so he delivered his already legendary riposte. Yes, it is difficult to imagine Jim Rosenthal saying it.

Merchant has come out with some memorable lines in the four decades this old sports journalist has held a microphone. "This makes Cinderella seem a sad story," bellowed Merchant as the rest of the world were open-mouthed when Buster Douglas, the previous quitter who had been abandoned by his own father, knocked out Mike Tyson.

Merchant had history with Tyson, just as he did with Don King, who shamelessly tried to overturn the Douglas result. It reached the point where Merchant refused to interview promoters as he was sick of providing a soapbox for their sales pitches. King was furious with Merchant, who told him: "Don, you need to be interviewed like everyone else needs to breathe." King agreed. But then, he would.

"If Don King was a city he would be Las Vegas," or so the saying goes. Merchant stood up for all of us who believe a more appropriate analogy would be Gomorrah. God bless HBO, which has stuck by Merchant, even when King was on his case and reportedly lobbying for his P45, even when he has dared criticise HBO's own boxers. Saying that, it was not going to renew his contract in 2007 until a public outcry ensued. Merchant's enemies inside the sport are infinitesimally small compared to the number of admirers outside.

Merchant has always scythed the nonsense, cutting a pathway through the stuff in America they call "the BS". He calls out phoney fights as phoney and challenges the fighters immediately. After Vernon Forrest was awarded a highly contentious decision five years ago he embarked on a list of thank-yous which would have sounded excessive on Oscar night. When Forrest had finally finished, Merchant piped up. "Would you also like to thank the judges?" he said.

Reputation and standing mean nothing to Merchant if he doesn't like what he witnesses and senses the armchair fans feel the same way. So it was with Mayweather at the MGM Grand. This confrontation had been coming a while, regardless of the Mayweather-HBO bickerings. Back in 2006, Merchant asked Mayweather: "D'you think that was particularly entertaining tonight?" Mayweather flew off on one, defending the bloodless shut-out of Carlos Baldomir by saying: "I'm the best at what I do." Maybe he is, but it was Mayweather who hailed himself as an "entertainer" and a "gladiator".

And there's the point. Merchant remembers all the promises, all the claims to immortality, all the baloney – and, when required, he throws it back at them. In an age of rampant sycophancy where the TV channels are so blatantly complicit in flamming up all the unsubstantiated hype which is slowly killing the sport, Merchant is a glorious blast of reality. The household name with a silver quiff might not be universally popular because of his ego; but my guess is an ego is rather handy when stepping up to tackle these brutes.

Mayweather refers to himself as "a great", but surely real greats don't wallop fellow fighters when they aren't looking. And they certainly don't go around telling octogenarians "you ain't shit". Merchant suspects Mayweather planned last weekend's flare-up as a means of avoiding the Pacquiao question. Well, he was successful on that score. But Mayweather should be aware Larry will be waiting. That's one match Floyd would not dare dodge, now would he?