Interesting topic...
I think this fellow has the right of it, personally (though I'm not sure I'd take him at face value, it's worth looking into closely):
The disconnect many seem to be having is due to some "it's wrong to hit a woman" rule.
In general, this kind of a bad rule because there are either many exceptions, or you have to accept pacifism and victimization as your only recourse to any number of scenarios. Once any rule has to have that many exceptions, it's not much of a rule. The spirit of the rule might be good (don't beat your wife, asshole), but the letter of it is piss poor (be obliged to let her hurt or kill you).
I'd say it's wrong to hit anyone in aggression, not just women. If events played out in such a manner, in this instance, gender equity means hitting the woman.
HOWEVER, it is worth noting that without strong evidence - the parking lot video surfacing, an impartial witness, etc - his "I hit her in self-defense" claim is unsubstantiated and his own character and record will be what a court / jury would look to.