That's the biggest load of rubbish I've ever heard.
Talking about "guilt" - are you, as a United fans responsible for any of the chaos caused by United fans when hooliganism was rife in the game? Innocent fans beaten up or stabbed, property looted or shops smashed up in away days in Europe or in the UK? I suspect you'd think you weren't.
This isn't about "free speech" because its not about having an opinion or discussing an issue with any actual interest. It's about a lot of grown men, most of whom who I suspect couldn't tell you anything about the actual events of Heysel/Munich (or whatever) trying to get a rise from another group of similar morons.
It's not people having and expressing a view on a historical event - it's mindless mob mentality from people who should know better, and often (as with the Chelsea "fans" in Paris the other week) are all apologies when they get singled out for their behaviour.
This kind of thing is what's wrong with football. There's still racism, still hatred - all for absolutely nothing. It's sad and it puts me off taking my kids to see my team and that's a real shame.