I dunno, I'd usually say kick his ass but I had a simple bus problem escalate to something huge.
When I went to college some kids sitting across from me and my friends said to one of my friends, "what's your problem? Got a staring problem?" and said he was gay and all that stuff. I interupted and asked everyone in the back of the bus if they knew why this punk kid was wearing a cast (he had one with a sling), and people thought I knew the guy when I asked that. I said it was because of "too much jiggin" and everybody was laughing at them. They said they'll beat the crap out of us blah blah blah so I get up and then use the back of my hand to lightly slap both of their faces and said "What are you going to do? What are you going to do?". They shut up for good and when we get off the bus one of them kicks my friend's back and he was leaving.
Months later I some guys got on the bus and sat beside me and one said that he heard I was talking to his girlfriend and stuff. I didn't know who he was talking about (found out later, some girl who came up to me and started this whole conversation on how she's going to Hawaii

) and I asked him if there was a problem with that. He tried to stir up stuff but I totally made him look stupid. Then out of nowhere when the bus stopped at a stop he elbowed me in the face and him and his crew runs off. I grabbed one of the last guys and told him he and his friend should be glad I was fasting (I don't know WHY I said that it must have seemed really retarded to the that guy, but it was true, I wasn't as angry as I should have been).
Anyways I move out of Red Deer months later and a couple months after moving I hear my friend was beat up into a Coma. Apparently it was these guys who did it. My friend got a Diploma in computer programming and he literally forgot all of it and he had to go to NAIT again to relearn that stuff. When he first came to, 2 months after the beating, he couldn't even recognize his own mother.
It was insanely retarded how these low-lives could take something so personal. I could easily take those guys and my friend apparently did too, he cracked a few ribs and fractured a wrist of one of the 7 guys who attacked him. But that's the thing, the odds are never even. Especially if you're dealing with the Chinese in Calgary heheh. So I'd study the situation more closely. My friend and I plan to still get those guys in Red Deer and in time we'll do it. The more time passes the more sweet it will be, and we're in no rush. Heh, maybe this will incriminate me...well I can always edit.
In the meantime if I were in your boots I'd be fuming and thus I'd try to find out more about this person and call in some fake tips to Police about him and say, drugs. I wouldn't be surprise if he was guilty of something. Anyways, that way he doesn't know it's you and you're still getting back at him.