TL;DR the former free speech warriors got the whip hand.

Meanwhile, once they fell out of power, the Right became the rule-breakers, the transgressors, the pranksters, the folks who said outrageous truths, while the Left turned into hall monitors, snitches, and finger-wagging moralists that made The Church Lady look like G.G. Allin by comparison.

This is not because of any inherent puckishness on the Right or censioriousness on the Left, but because of their relationship to power.