Guy Stagg, writing for the Telegraph, discusses this as it relates to the Occupy movement:
The Occupy protestors do not represent people of all political outlooks and from all walks of life. Equally, their causes and concerns are not universal. Instead they are a bunch of pressure groups, fringe campaigns, and partisan causes, dressed up as a mass movement. Yet despite this fact, they pretend to speak for us all.
That pretence is the real objection I have to the Occupy Movement. The protestors think that they are on the side of goodness and virtue. So they are quite happy to assume the support of a general public that was never even asked. More worryingly, they are quite happy to ignore police eviction notices, and mock the traditional model of democratic accountability.
The Left has laid claim to morality. And the cultural establishment has let them, indeed it has all but supported them. But the truth is, you don’t have to be Left-wing to be good.