Its an extremely complex situation with multiple factors. not all men and bigger or stronger than women.
Its never ok to hit regardless of gender, unless your life is being threatened in some way...
If a women was to hit a man then she would be entirely in the wrong, does that give him the "right" to hit back... depends... If the only way he can "escape" is to hit back in order to then flee, self defence is self defence.
If a women hits just once and backs off and the man can leave without the need to hit... then obviously that's "morally" best. The old saying and eye for an eye makes the whole world blind springs to mind.
I would say a women would never be judged for hitting back in self defence, so a man shouldn't be either.
Reality is in this situation instinct would take over... "fight/flight/freeze" anyone being attacked will have instinct take over, anyone women who went to "fight" wouldn't be judged as doing anything "wrong" so its not really fair to say a man is wrong either.
He should be advising his daughter never to hit, unless in self defence, but not "because you'll get hit back" simply because... assault is illegal and decent humans don't do that!