This ^ ... Is indicative of emotional manipulation. If he monitors his behaviour in front of his parents (that is, in situations where his anger can get him into trouble), then he knows it's wrong and he is capable of stopping himself. Rather, he knows that he shouldn't be doing it. But he likely feels justified for some reason or another, so he chooses not to stop himself. Such a technique is quite effective in controlling people... Depending on the person, of course.

It also happens to be one of those manipulative techniques that even I know is unethical. So, yeah, cut him loose.

But, out of curiosity, this is the same guy who agreed never to look at or speak to other women?