there is no point? absolutely no point in making the dlc exclusive.. your going to release it for ps3 anyway? your going to make the same amount of money wether you release it now or in a couple months? well actually probably less because people will be so pissed off they will dump the game. its just so stupid?! what does it prove?! it wont make you more money and it will make more people hate microsoft? honestly what is the point!?
This is a fairly common practice. the UFC games had exclusive fighters to each platform, Microsoft bought the rights to Shenmue 2 so that it wouldn't get released in North America on the Dreamcast (only on the original Xbox), Sony used to always get the GTA games first (before GTA 4), exclusive content on cross platform games is not rare in any way. Whoever's got the fattest wallet gets the cooler things first. It's actually a good life lesson. It's the same thing as asking "why does my neighbour get a nicer car than me?". The answer: because they paid extra for it.
That said, PS3 and PC owners can be happy that, as one poster mentioned, the 360 owners will beta test the DLC first. When the others get it (and you will, don't worry, there's money to be made). Microsoft wanted the exclusive deal so that people would say "oh, I'll get the Xbox version (if they have a choice), it will have the first DLC available!". This means more people buying Microsoft points, which means more of a cut for Microsoft in the end (no doubt they get a percentage of every DLC or XBLA game sold).
So, in short... yes, there is a point. It's called capitalism. And it won't hurt PS3 or PC sales of the DLC one bit for Bethesda, because those who don't have a 360 who normally buy DLC will still buy it.
Also I don't think Microsoft is worried about anyone hating them any more. It's so trendy to hate Microsoft, you might as well put on thick rimmed glasses and a flannel shirt while you do it.