In this framework there is no such thing as “a man” but rather “being a man.”

But to answer your actual question I think proponents of this view would ask you to think about it like this: if a professor vindictively fails you for correctly contradicting them, did you really fail?

Certainly it’s possible to be in a situation where the Other’s understanding of manhood contradicts one’s understanding of themselves. But important to remember you’re only “not acting as man” in this person’s understanding or within your shared understanding with this person. So they can only really accurately say “you’re not a man to me.” This is the case with everyone.