This argument is entirely dependent on context and is very situational.
What caused her to hit him? If he cheated on her, then he deserves every ounce of physical punishment he is going to get from her, and he should not fight back because he's immoral and pathetic for cheating on her.
But if it's a situation where she is just angry and the guy hasn't done much to provoke such, typically a male is physically more imposing. The male should always attempt to restrain the female until it escalates too far. And in that context, I mean if she resorts to ulterior forms of violence against him, like using weapons as a means to hurt him.
But again, it's entirely based on the context. It's best if "no hitting" was just the placeholder in all of this, because men hitting men, men hitting women, women hitting women; none of it should happen in my honest opinion. Violence is usually just an offshoot of pent up emotions or frustrations and it isn't even typically directly related to the person whom the violence is directed towards.