I doubt you can ever, "shame", these people with this though, as A) they simply do not recognise it as being wrong and B) feel utterly confident that all around them feel exactly the same as themselves. What 's more, they are unlikely to be disabused of this by the people around them as, sad to say, many of them do.
Unless this idiot is outed I'm not sure exactly what the club can do to be fair, certainly as far as taking any direct action is concerned. As said in the first paragraph, I doubt he will be 'outed' by his friends for all the same reasons. The club should come out and condemn it outright, of course, and IF the culprit is ever uncovered then they should be banned forthwith - or even sooner.