Even if you look at all this objectively the guy's still a douche. Of course there's back slapping because we're all friends here. Are we supposed to be robots that don't encourage each other. Like a previous poster mentioned, walk up to a group of friends and start being a d!ck and see if they don't start making fun of you and encourage each other to do so. That's why manners, and being mindful of your approach to a close nit group of strangers, are valuable. I know this is redundant, but apparently not to Captain Strict Rules Douchebag.