Expect some foul language, yes. But people take it to the extreme and use the sporting environment as a crutch while conveniently forgetting they're out in public. I was at a Bills-Raiders game and a Raiders fan was there with his daughter who was probably 10 or 11. She was dressed up in Raiders make up and all, and to any rational person it was kinda cute. To a couple of drunken idiots, though, she was public enemy #1 and they called her a "little B word" twice before the dad stood up and confronted them. Like most idiots who would pick on a little girl, they backed down.
That's just one example of people going beyond just venting when it comes to cursing. There are plenty of others. Why should being at a football game make people forget they're still a part of humanity. Would anybody call an innocent 10 year old girl a little B word at the grocery store or the post office?