I guess you could see it that way but at no time has Beast said or pointed as that was the real reason he left. You're kind of inferring that was the reason. The way it was written was that Beast didn't want any part of a group with a leader that was willing to do anything(even sacrifice his own people) to win(save the mutant race) no matter what it was. When Nightcrawler dies he blames Scott because he was willing to put him in danger to protect Hope just like he did with Beast. That's not a personal thing but how you're running things.
Beast didn't like X-force but when he experienced first hand Scott sending people on pretty much suicide missions is when Beast was out.
But I'll tell you what, come down and will go to a Timbers game together and after some beers, walk the streets of Portland until we find Matt Fraction and ask him.
