The falsehood of "emasculation"

I wonder if the concept of psychological "emasculation" is, in itself, kind of a sexist idea. When people refer to a man being emasculated, they're usually alluding to him being undercut or browbeaten or belittled by a woman. But isn't that type of behavior generally inadvisable for anyone? People shouldn't behave that way toward others as an overall rule of courtesy. Why is it somehow "worse," to the point of earning its own classification, when a woman does it to a man? And why is that regarded as stripping him of whatever it is that makes him masculine--unless the assumption is that men should behave that way toward women, and so doing the reversal is acting upon an irreverence for social norms?

I'm not advocating for women to deliberately mistreat men as an act of protest against gender roles. I just think it's notable that a woman being a jerk to a man is seen as revoking his masculinity, whereas a man doing the same to a woman isn't judged as revoking her femininity or her identity as a woman. Yes, it's often frowned upon, but "effeminization" is not a commonplace word--unless it's used to insult men for "acting like women", because society deems femininity a negative trait. "Effeminization" is used as a synonym for emasculation, not a counterpart to it.