Self-hating cultures

In Markku's blog there was a post on Western culture's self-hatred as opposed to some Asian cultures, and some conversation about it. One of the comments there made me wonder, though: the person suggested that the Western culture's tendency to disparage itself stems from the romantic idealization of primitive cultures and of the "noble savage", which was funny because I had always assumed it was the other way around: people despised their own culture to begin with, and then invented the "noble savage" in order to have something else to admire.

Anyway, I don't know enough on the matter and did not participate in the conversation. I don't like the oh-western-culture-is-so-evil-and-third-world-cultures-are-so-much-better crowd, but I think that this attitude is not as widespread and one can imagine from the media, and is fairly superficial even in those people who profess it (how many of them actually give up the Western civilization and go live in some third-world shithole on the equal footing with locals?). However this made me think about the following thing: the supremacists of any kind (white supremacists, black supremacists, Russian, Jewish, Muslim, you name it), at least almost all the ones I've seen so far, all hate modern Western culture too, or indeed modern culture of any kind. They tend to idealize the noble savages as much as the generic western-culture-hater crowd, with the only difference being that for the supremacists the only savages that were ever noble were their own ancestors. I mean, check out some white supremacist sites sometime. It's almost never that you see anyone there who actually likes the current culture of white people. Everybody there is pretty much saying "everything was going so well when our ancestors were the Germanic tribes conquering Europe and then Jews and Blacks showed up and spoiled everything".

Wonder why is that?