If I hadn't read the piece you linked to then I'd have assumed the 'tightsarenotpants' site was hipster mockery. The people I've seen wearing leggings/tights here are the American Apparel crowd, so it seemed like there was a definite overlap with hipsterdom.

That said, I think this sort of situation can combine legitimate criticism with classism etc. Yes, I can totally see this. Historically in the UK and North America, enforcing 'public decency' has involved policing the sexuality and dress of poor women, so it's a difficult area.