I think I mostly use it as an ironic term, but I do try to not use it. I always found the term irritating when it was used in a serious context. It reminds me of my mother always telling me "be a lady!"
I don't think it has anything to do with how masculine the guy is either. My father, the ex Air Force military man, hates the phrase. I've never heard him use it toward any of my brothers despite how much of a jerk he can be. Like my old man, I usually just say "act like an adult" "be the bigger person"and the like depending on the situation and who I'm talking to.