She definitely doesn't want his ass kicked and I have no intention of doing it.

It's more a case of should i talk to him about it, make sure he is aware of how he is behaving, how she really feels, and make sure that he is not rationalising his behavior. Maybe him having someone to talk to would help in itself. This wouldn't be such a big deal if they weren't both such good friends.

But even though they are friends, perhaps it's still none of my business.

I don't know, was round their house tonight for dinner and all seemed fine, they seemed great together, telling stories and both getting excited as they each tell their part, like a normal happy couple. It's not like she lives in fear or anything, it's just from time to time he acts like a complete cunt. (I feel I'm over using that word but it just sums it up perfectly imo)