Mencius Moldbug traces back the lineage modern progressivism to the Puritans, and you can still see the effects of this lineage in its illiberal totalitarian righteousness[1]. They were briefly the supporters of liberal principles like free speech and open debate when the movement was young and had no power. Like all movements which have grown to power, it now seeks to drive all dissent into the shadows by making dissenters bear a heavy price, a scarlet letter, if you will.

[1] http://foseti.wordpress.com/2014/01/06/review-of-unqualified...