Dead wrong about what?
I'm not a therapist, so I can't directly help you, but indirectly... you should see a therapist. 'I used to think it was just some Michigan fans who are bad, but now I know it's ALL of them.' The fact that people can say that kinda thing (about any group) and not realize how ignorant it is.... well, yikes. Blanket statements and stereotypes are the product of irrational hatred and lazy thinking. You're better than that.
As a Michigan alum, one is easily exposed to more anti-Michigan BS and whining than Michigan haters are exposed to their imaginary affronts. Usually just boils down to jealousy and envy, and then an exaggeration of half-truths inflated with hyperbole. Over and over and over. I've seen it for 25 years. It's a psychosis for some.
So, no, I don't believe your story word-for-word, especially since it went from getting cursed out to now... getting stitches? Huh? Did you press charges? And yes, having had absolutely no interaction with the guy up to that moment, I had a stranger put a cigarette out on my arm when I was 5. It didn't make me hate any college or sports team, just individual human beings who are willing to put a cigarette out on a 5 year old's arm. Maybe I'm doing it wrong though.
As for insults, step back and look at all the hatred you've posted about the Michigan fanbase in this thread, filled with insults that you've applied as a generalization of the entire UM community, as if that's ok in this thread because it's not explicitly aimed at an individual.... and then ask with a straight face to not get flak back. Pretty ridiculous.