Here are two articles by English writer Steven Wells who lived the last years of his life in Philadelphia, which argue the opposite:
Just to get some actual stats in the discussion, here are the number of incidents at 49ers games during their 2010/11 season and here are the arrests at English football in 2013/14](https://www.gov.uk/government/statistics/football-related-arrests-and-banning-orders-season-2013-to-2014). Comparing crimes across countries is extremely hard as anyone who has witnessed gun control debates, but 664-187PC / 245PC refers to attempted murder/assault with a deadly weapon in the California penal code. There were 9 of these incidents in the above table, if we assume the 49ers sold out their 68,500 for the 12 games they hosted that season it gives us a attempted murder/assault with a deadly weapon rate of 1.094 per 100,000 attendees. The violent disorder rate (which I suspect is a much looser definition) at Premier League matches was 0.495 per 100,000 attendees.
I know the 49ers do not have the best reputation, but even with this probably looser definition, the fact that away fans count towards a teams' arrest rate even though they don't count towards home attendance and that arrests on trains also are counted only five teams in the Premier League have a higher violent disorder rate than 1.01: Liverpool (1.60), West Brom (1.35), West Ham (1.27), Chelsea (1.12) and Swansea (1.03).
Maybe the conventional wisdom is out of date?
