The gist being... Moral superiority is like being a Nirvana fan; once everyone has caught on, the early adopters need to find a new band.
Well, this doesn´t really challenge the idea of legitimacy, nor acknowledge that early adopters are a shallow and vain minority. However, someone on here did claim that no progress had been made against the patriarchy, which had merely found new and more subtle ways of controlling women. Interestingly, this phrase crops up here almost exactly.
www.iea.org.uk/blog/the-economics-of-political-correctness