Totally aside from boxing, just judging him as a human being, there's enough direct quotes from him to confirm he's an arsehole.
When people have hero's, they can overlook any of their misdemeanors. I'm probably guilty of it myself to an extent with regards Gazza. But then in this instance I'm only judging Gazza by what he did on the football field (okay and a few interviews and off the field antics), I'm not advocating him hitting his wife though. To non football fans Gazza is probably a bellend.
I'm sure to boxing fans Ali was a god, but to a non boxing fan, judging him purely by the things he said, he was a bellend.