I'd say it's cowardly and sly when you know the other guy can't/won't punch you back as he's got a Heinekin cup final next week and can't afford to get cited. Ashton didn't hit back at all, just tried to push him away and Manu kept on hitting him, and the intent was obviously to injure and knock him out - when you're that big, you've punched a guy twice and he's just trying to move you away, and you smack him like that, that is totally malicious and intenting real harm.
Dunno how much you know about punches and the human body, but getting punched that hard in the head could do some very serious damage.
Personally I hope his ban is such that he can't play any part in England's games until after the world cup.