Personally, I think the rise of identity politics and the cult of victimhood is where the problems started
Used to be, folks would lobby for an issue, and have a definite goal in mind: once reached, everything was good. Identity politics changed that, as "the struggle" became the central cause for living.
Using one example Fistful mentioned: gay marriage. Most of the gays I know were actually happy with the idea of civil unions: "I can go and get all the same rights as the straights get, just as easily? Then we're cool!". Unfortunately, a fair number had made the fight so central to their lives, that they didn't know how to live without it. Add in the whole victimhood game, and things went crazy.