Liberal commentators on both sides of the Atlantic have been quick to blame the UK’s general election results on Labour going too far left. In the United States, Democratic Party centrists are preoccupied with warding off Bernie Sanders and, to a lesser extent, Elizabeth Warren. That liberals would seize an opportunity to chastise the left is no surprise. Anti-leftism plays the same role in today’s society as antagonism towards heresy played in the Middle Ages, and is animated by similarly ignoble motives. Nevertheless, Labour’s defeat has profound implications for the left.