Some speculation:

Tolerance–of differing religions, behaviors, lifestyles, attitudes, political ideologies, speech patterns, languages, etc–brings a wide range of benefits. Tolerance facilities the free exchange of ideas and goods, and in the long run helps produce innovation and prosperity. Mill is basically right about all this. Of course, not everything should be tolerated–some things should be criminalized and some things should face social punishments. But without specifying the exact limits of toleration, toleration is a good thing.

It seems to me, though, that tolerance is a public good and faces a public goods problem. In general, my individual disposition to be tolerant or intolerant has no significant effect on the overall culture, on the creation of music or art, of innovation in food, philosophy, living arrangements, sexual behaviors, religious ideas, or whatnot. Whether *we* are tolerant matters a great deal; whether any of one us is tolerant has only micro effects. (Being an asshole to your new Muslim neighbors or shouting down non-Marxist students in your English class hurts them, but the general social effects of your individual behaviors are negligible.)

Here’s the problem: While we all benefit from having lived in a tolerant society, we have individual incentives to free ride on tolerance. A fortiori, we have incentives to be intolerant.

Most people belong to a number of identity groups, many of which are defined and held together by various beliefs about culture, social practices, political ideology, theology, and whatnot. When you belong to those groups, you generally prefer to have higher status rather than lower status. You can increase your status by demonstrating stronger than normal loyalty and commitment to that group. To do that, you might not only A) compete to adopt and exhibit ever stronger, more extreme, or more “pure” versions of the group’s favored beliefs and behaviors, but also B) demonstrate your commitment by showing extreme aversion to and intolerance to outsiders, especially those in the “enemy” or opposing groups.

You see this all over. Metalheads who say how they can’t stand to even hear pop music. Libertarians who only date other libertarians and who brag about their “purity test” scores. Leftists professors who say that platforming conservative ideas count as violence. Conservative Christians who brag about putting down Muslims. The 800 people who signed the Tuvel letter. Everyone on Facebook bragging about how they refuse to associate with, do business with, or serve those who have certain beliefs or attitudes they find repugnant. The continuous strawmanning and de-humanizing of people in opposing groups.

En masse, this kind of behavior tends to be socially destructive. It encourages others to tighten their connections to their own gangs and respond with the same kind of behavior. It leads to increase incivility and factionalism. If people declare war on you, you better build your army.

But individually, intolerant behavior wins you status and esteem among your group, unless you belong to one of the rare groups which values tolerance as a virtue.

I suspect very few people actually value tolerance itself. When the typical member of Antifa reads about, say, Puritan society, they don’t really think, “Oh, the problem with the Puritans was that they were too intolerant.” Rather, what they really think is more like, “The problem with the Puritans was that they were wrong about right and wrong, so they were intolerant of the wrong stuff. Puritans? Good methods, wrong targets! They should burn conservatives, not witches!”