Re: Bones, season 4
Booth is at his most dangerous when he's defending others. He isn't gratuitously violent. The ice cream truck thing was more of an aberration, an extreme reaction to stress. (And even there he blew off steam in an extreme way without hurting anyone or putting anyone in danger. He's a good shot. He hits what he aims at.

)
In the hockey game the other player was at the very least bending the unwritten rules, going after "Booth's guys" in a way that was not acceptable and which both parties
knew would have consequences. (Especially given the ref's refusal to enforce the
written rules.) He used an amount of force appropriate to the (repeated) violation of the implicit compact that all the players recognized.
Now if Booth started wailing on the same guy when he
wasn't protected by pads and they weren't playing a hockey game - say if he cut into line ahead of Booth at the diner - then I'd see it as a real problem. As presented I see Booth as a man with a lot of rage who knows how to channel and control it, and who only expresses it in defense of others. He wouldn't have gone off on that guy if he's simply been the target of some hard checks himself.
OTOH, Heaven help anyone who seriously threatens Temperance when Booth is around. If she's ever kidnapped I wouldn't want to be the guy who knows her whereabouts and who draws Booth as his interrogator.

Regards,
Joe