And that difference is what exactly? I'm not seeing such a clear difference between denying a fact and being insulting to warrant banning one but not the other, especially when banning the other would stem terrorism like this.
Let's say I believe wearing hats (of any kind) is deeply offensive, and my religion says that anyone who wears a hat must die. Should you -- and everyone in your society -- oblige me, just because I have a belief based on nothing but faith?
Conversely, consider this example: blacks in America believe they are being unfairly discriminated against, and pretty consistently fight for better treatment. Well, it turns out they're right; they
are systematically discriminated against. That's pretty important to whether I support their cause, don't you think? If the evidence showed that black people were not discriminated against in any way -- if, for instance, we found that black people had no more trouble getting jobs, no more trouble than other races with the justice system, no more trouble getting housing -- then I think a reasonable person would say "No, this is all in your head, we aren't going to support your movement just because you feel discriminated against. You have to actually
be discriminated against."
Generally, we require people have a reasonable foundation for being offended before we oblige them.