It could easily be argued that he retaliated against her punch, not defended against. In which case, it would be a fight and both would be in trouble.
This is what I actually think the fair outcome should be.

I was going to include the caveat to exclude children from the argument, but I thought it was so ridiculous that it didn't need to be explicitly stated.
But yes, children are a reasonable exception. The elderly and handicapped as well.
I don't think a healthly adult woman falls into the same category of defenselessness as these groups.