Trump’s presidential campaign succeeded in part because the candidate challenged these second-order taboos (especially as they show themselves in the phenomenon of political correctness) — and liberals have responded in part by attempting to reinforce the taboos, mostly through name-calling that boils down to the assertion, “You can’t say that!”

Sometimes this assertion is merely rhetorical. But at other times, in the statements of various courts that have blocked Trump’s policies on immigration and sanctuary cities, it’s backed up by the force of the judiciary. (In France, Marine Le Pen faces a similar dynamic, with nearly the entirety of the French political establishment closing ranks against her to convey the message to the electorate that voting for the National Front is simply unacceptable.)

The problem with telling people that they’re not allowed to get their way on certain issues is two-fold. First, as we’ve seen with the Trump phenomenon, controversial opinions don’t just disappear when members of the establishment rule them out of bounds. They often reassert themselves later, more powerful and more radicalized than before. And second, the excommunicators may become fond of the tactic and apply it to an ever-expanding range of issues.