But Carvalho's death raises extra questions. Here is the Irish Times, describing the last moments of Carvalho's fight with Charlie Ward in the Total Extreme Fighting event: "Ward...instinctively follows with a clean right to the side of the head, another "good" punch that knocks his opponent senseless. Carvalho slumps down by the side of the ring. He is helpless and unable to defend himself. Ward senses his opportunity and falls on to him. He partially holds up the collapsed and dazed Carvalho with his heavily tattooed left arm, which fulfils two functions. It presents a clean shot to the right side of Carvalho's exposed head and face because he is held off the canvas.
Ward also uses his opponent's body as leverage to get power into his right-handed punches, which rain down. Seven of Ward's nine punches to the right side of Carvalho's head and face are long arcing blows, full punches. Carvalho does little to protect himself other than put his arm across his face. The referee stops the fight and the crowd explodes in delight."
Carvalho was treated by a doctor but died later. The key words are "helpless and unable to defend himself". It is MMA's achilles heel - the ability of one fighter to keep beating another when he is down, what is known as "ground and pound".
It completely crosses the line applying in all sport - respect for the opponent. In all other sport, a fallen opponent is off limits. Only in MMA do you see the aggressor fall on the prone opponent and smash him some more. A boxer has to go to a neutral corner after a knockdown. Hitting an opponent when he's down is one of the greatest crimes in a boxing ring. In rugby, shoeing a player on the deck is a sin, especially if the head is involved.
In my gym this week, the TV showed an MMA bout where both fighters were on the canvas, wriggling and joined like some grotesque human beetles, trying to gain a submission hold and peppering each other with blows. Both were covered in blood. The Coliseum came to mind - but there is no glamourised Hollywood treatment of the gladiatorial contest here. There is no athletic beauty in the ground and pound, just the brute, bloodied desperation of two human beings - and it can go too far, a la Carvalho.
MMA has come a long way from primitive beginnings; there is little point in calling for a ban. It has become a multi-billion dollar industry with legions of fans all over the world, many of whom appear to enjoy the spilling of blood. Some can be seen howling for it outside the cage that MMA has worked so diligently to remove from our vocabularies - cage fighting ("human cockfighting", US war hero, senator and Presidential candidate John McCain called it) being a much less acceptable term than MMA.
Its civilised face includes new rules, officials, doctors, cornermen. It draws fans tired of boxing's tarnished credibility and wrestling's dance moves. It is run by a slick corporate entity which has steered the sport away from the factions, challenger dodging and self-serving hype which has wounded boxing. MMA fighters are paid a pittance in comparison to professional boxers and are tightly controlled.
Which brings us back to Carvalho, dead at 28. MMA icon Conor McGregor tweeted the ref could have stopped the fight earlier. But it's not the ref, it's not the doctors, it's not the fighters, nor even the businessmen behind the MMA. It's the fans. People like us are the reason MMA exists and the only way to stop it is not to watch it.