Yeah, without labouring the dog analogy too much (well maybe just a bit!), but this other guy is trying to be top dog within the group.
It might be just testosterone-poisoning
but he probably wants to take control or at least score points and undermine your friend.
He is getting kicks from creating his own little band of followers and showing up the boss.
He badly needs to be smacked down, publicly (of course I mean that metaphorically, I'm not suggesting an actual slap......
not yet anyway
).
To tell the truth, at different times I have been on both sides of this equation, and the only thing that works is for the real top dog to show his teeth and maybe even bite a bit.
I know I have now totally laboured the dog metaphor
, but its one that makes sense in this scenario. I blame Purple, he started it
Sounds like he has made a good start, but don't just pick on the followers, definitely smack down the ringleader the very next time he tries anything on.