I can see this argument going round in circles forever?
Who cares who started it?
I was of the opinion that it was because the Hellfire Legion were moving in on Gamma to hit SCRA and Phantoms that TBH got involved, and AW got involved because the HF did, due to their alliance, rightly or wrongly. But, it really doesn't matter.
Everyone wants to be the 'good guys', the 'heroes', even when in-character, these characters regret 'missing slaughter'. We all want to be the heroes but we all know that a large amount of the time, it really depends on where you're standing. You aren't going to convince the other side that they're the bad guys. Unless they're Phantoms.