A proper argument takes intellectual vigor, nimbleness, and sustained attention. If carried on long enough, it can push both parties to a deeper level of understanding. Oxford debaters hack away at each other for something like two hours. Socrates could sometimes go on for weeks. But who has that kind of time anymore? Better to just shut things down quickly, using one of a new array of trump cards.

Want to avoid a debate? Just tell your opponent to check his privilege. Or tell him he’s slut-shaming or victim-blaming, or racist, or sexist, or homophobic, or transphobic, or Islamophobic, or cisphobic, or some other creative term conveying that you are simply too outraged by the argument to actually engage it. Or, on the other side of the coin, accuse him of being the PC thought police and then snap your laptop smugly.

In the art of debate avoidance, each political camp has honed a particular style. Conservatives generally aim for the prenup approach, to preempt any messy showdowns. If you want to join the club, then you have to sign a contract or make a pledge—no new taxes, no abortions, no gay marriage—and thereafter recite from a common script. Progressives indulge a shouting match of competing identities that resembles an argument but is in fact the opposite, because its real aim is to rule certain debates out of bounds.

We’d like to blame social media for this development: it’s hard to carry out a Socratic dialogue in 140 characters or less (and yet so easy to bring down mass outrage on an offending voice). We’d like to blame academia, where easy outrage can make you popular. We’d like to blame some distant radical fringe. But the truth is, declaring certain ideas out of bounds has led to some pretty powerful victories. The left has made it politically and socially treacherous to oppose same-sex marriage. The right has done the same with raising taxes. The tactic has lately proved surprisingly effective, but it comes with a high cost: also politically treacherous is empathy, or humility, or actually hearing out your opponents.