I do not enjoy physical fighting outside of a sports environment.
In all my life I haven't started a single fight, but I got involved in some, had my nose broken a few times, got stabbed, got my arm broken, my hand, a cheekbone, lost a few teeth, the list goes on ...

Just apply some common sense, ask yourself:" is it smart to hit a person, X lbs heavier and Y inch taller?" - if your answer to that question is "yes", then that person will have to (and probably be able to) teach you a lesson.
If you think, you deserve the right to hit people randomly, because of what reason ever, then you are wrong.
This is called "assault and battery" and illegal, but there are no countries that I know of, where self-defense is not allowed.

IMHO Joe Mixon did nothing wrong, didn't exagerate his defense, so he got punished for being a big man. That's just the opposite of equality and to punish him, but giving her a "get out of jail free" pass is sexist as fuck, as it inheriently indicates women are not only weaker, but as well too stupid to know it.

P.S.: I'm a 6'6", 300 lbs male, who used to work as bouncer.