In the words of Snape: clearly, fame isn't everything.
There might be more to the story, but from the sounds of it, the guy decided to attack two innocent kids. How wonderful.
The kids were possibly being a bit annoying, but there's other ways to deal with those things. Besides, they were just that - kids, who actually admired the player enough to want his autograph badly enough to wait.
I know celebrities probably get tired of being interrupted for autographs. But three men against two kids... that's not necessary, no matter what.