How is it a career limiting move? It's not like he's crossing a picket line. It's not like the press is to be believed...But if one were to believe them, McGee is stating the obvious.
Not everybody in this union has been the receipient of millions. Some, like McGee, think they probably can't afford to waste a bunch of a limited window of opportunity banging their heads against the wall. If things are the way they appear publicly, negotiations are going nowhere.
This guy is due for a huge payday. Probably doesn't want to waste a lot of time spinning his wheels.