It's assault whichever way you slice it.
Yep, to a guy who deserved it? evens it out doesn't it?
Never ever hit a woman unless she is trying to kill you but stamping on someones head while they are down is a no no.
What about stamping on the head of a guy who punched a woman in the back of the head?
Stamping on a guy who has no chance of defending himself is EXACTLY as bad as punching a defenseless woman, both are completely in the wrong.
I agree, however stamping on a guy who's MASSIVE... and just KO'd a woman by punching her in the back of the head is another matter

but is stamping on a mans head the chivalry that girl wanted in retaliation?

They're **** heads. The ones I've met (and know) all are, as are most Muay Thai fighters.
This just in, Muay Thai makes you a **** head.