They, especially Stein, have gone on and on about how stupid they think he is… and Stein at least knew that he had had hallucinations of Snart before, yet just bit into him for talking to what he thought was a hallucination. If he needed to choose between that and an actual alive Snart, there really was no comparison.
As far as I know Mick is a grown up man, not a teenager who can be excused for his bad things just because his feelinga are hurt, so don’t try to portray him like that.
Mick choosing his old partner and joining the legion of Doom is totaly on him and it was his own selfis choice to want to change reality, and Stein saying some bad stuff to him is not comparable to what he is about to do to the world.
And as it seems from the trailer this wasn’t his smartest move at all, after everything he’ve seen from the legion he should have known better, so maybe Stein has a point.