I can easily see this being true. I can also see people not being totally 'innocent' but still not enough to warrant what the police have allegedly done. This is exactly why I'd be avoiding boozers in and around the ground and boozers with a reputation in town when a 'tasty' team turn up. Not worth the hassle.
By not being totally innocent I mean not doing exactly what the aggressive police tell you to do. If I had a beer in me I could easily see myself telling them to do one. Then they've got their reason to pile in that they've been waiting for and there we go. Not worth it, so I avoid it.
Looks like I'm a shirter.
By all accounts you've always got a beer in you !