Before I come to the UK I was weary of football violence. I have since been to at least 50 games in a variety of stadiums and never encountered any violence or even been threatened. Part of that is because the fans are separated, but, thst said, in Stoke and Fulham, for example, my friends and I were able to drink with opposing fans in the opposing fans' pubs while wearing our Spurs shirts and had a great time. The reactions to the violence of the 80s have made English grounds very safe. I have seen worse at rugby games in New Zealand and frequently hear of much worse at NFL games. Heck, 4 people were stabbed last week at a game,weren't they?
There are certain places I wouldn't go to support Spurs: Rome being an example. But, without doing any research, I'd guess that the UK, Germany, France, Spain, Portugal can go for seasons, if not decades, with barely an incident.
As Glasgow says, violence in the stadium is almost unheard of.