I don't blame him at all for what he did. He didn't mug the guy from behind. He confronted him verbally, and when the kid with the racist shirt was smarmy about it, he got hit. I can understand why.
Did you see it? I didn't so I don't know whether it was this kid or another...doesn't really matter...they were both wrong and their Daddies ought to open up a can of whupass on each of them. Stupid is as stupid does, to quote a great American movie, Forrest Gump!
it really doesn't matter what the reasons were- he should not have been assaulted.
Why is it so hard to understand that what you are doing is hurting the assaulter by allowing him to think it's ok? How does this help him?
Another note: you are saying the black kid couldn't be "expected" to show restraint, right? Is it because he's black?