Well, I mean. Technically, Heiji didn't approve of senseless violence? But since it seemed like Trevor was gunning for a fight anyway, what was the harm?

Heiji brought his forehead forward and smashed it into Trevor's. Okay, 'smashed' might not have been the right word, because he was aware that human skulls could be a bit fragile and so he pulled the blow a bit.

This was fun, right? They were having fun.