Language Log has long been among my favorite blogs. The linguists who contribute to it are radical dudes with an extremely healthy attitude towards prescriptivism -- they despise it.
I do too. I think "correct" grammar is good and fine and I appreciate a graceful sentence, but I have encountered few people who are demonstrative about their horror at grammatical and linguistic "error" and who don't, at the same time, give me the sense that their interest in that subject is way of asserting their superiority to others, especially when the sentiment is couched in decline-of-civilization terms.
I would guess, furthermore, that for most of us, the sense of inherent linguistic conventions we've internalized is relatively stable once we reach adulthood. If that's correct, it's possible to think of an assertion of grammatical superiority as an assertion of superior education, which is one step away from an assertion of superiority based on class. I'm not saying that this is always the case, just that it behooves us to take the complexity of the issue into account before crapping on about what morons people are who can't distinguish between a restrictive and non-restrictive clauses.