The guy was in the wrong...he initiated the physical contact.
IF you grab a woman's ass or what ever she has every right to throw a drink in your face or shoot the bird at you for doing it...because grabbing her is initiating the physical contact.
Near as I can tell the dude was the one making it a physical confrontation.
All that said, if she had hit him first before anything else happened, I would fully support that guy retaliating.
If a woman hits a man it's easily fair game for the man to hit her back. All you Gallahads that think you can't get your ass kicked if you let a woman just tee off on you are operating under a delusional sense of superiority.
My brother, who is a cop, had a similar delusion until he got put into the hospital because he let some 4'11 chick tee of on him...she ended up breaking his jaw and permanently damaging his knee to where he still walks with a limp to this day.
On top of that, I saw women put men into the hospital with severe asskickings all the time when I worked for an attorney...you'd be suprised what women can do in some instances.
I'm sorry but if some woman comes up and hits me and I'm going to drop her on the spot. Unless I grabbed her ass...then again, I wouldn't just go grab some woman's ass. It's pretty disrespectful.