I grow tired of hearing about how awful American MMA fans are. Yes, there are many fans who boo at events, because they are drunk and ignorant. But I don't know of a place where fans are completely respectful at sporting events. Soccer fans everywhere are insane. Baseball fans, basketball fans, and hockey fans are all idiots. You have to expect that a bloodsport will draw some of society's less desirable elements.
The only fans I see behave well on a fairly regular basis are tennis fans and golf fans. The sport has to be steeped in a history of decorum to even expect laudable behavior from its fans. For crying out loud, even cheerleading competitions and beauty pageants have psycho moms, scam artists, Woody Allen fan club members, and Mean Girls wannable contestants to watch out for. Just a lot of crazy people in the world, no matter where you go.