It's a real case of both of them being wrong.
Here's how he SHOULD have handled it in my opinion. Ballboy wont give back ball, appeal to officials, get extra few seconds added to game, maybe free kick, I dunno? Make the guy look stupid on TV. But to kick him --- even accidentally (and I don't think it was: I think he had a sly knock at the kid) --- is unacceptable.
The ballboy should be dismissed and never allowed near the ground again.
As Manish Bhasin said, two wrongs do not make a right...
And now that idiot has almost 100,000 followers on Twitter? Are there that many stupid people in the world? Don't answer that.