There are two types of people in the world:
Those who believe in absolutes
Those who live in reality.
Anyone can do anything if the situation is right for it.
Honest men lie
Faithful men can cheat
Evil men can do good deeds
Liars occasionally tell the truth
Saying there is no way I would hit a woman is akin to saying if I was starving there is no way I would eat (insert something you hate). Possibly you can be that firm in your conviction, but in my experience its all talk.
Greg is probably in the wrong, but not knowing the situation or witnessing in person or the backstory behind what happened is a rush to judgement.