I think it depends on whether or not he has a justifiable reason for punching her. If, for example, he’s punching her because she verbally attacked him, then he’s wrong. If, for example, he’s punching her because she physically attacked him, then he’s not wrong. I don’t think I could draw a definite line between the two. Purposely breaking a valuable item of his justifies a punch while purposely breaking the rules of a monogamous relationship by having sex with another guy doesn’t. It just depends on the reason for the punch.