Mr. Pinker goes on to argue that when members of this group encounter, for the first time, ideas that he believes to be frowned upon or suppressed in liberal circles — that most suicide bombers are Muslim or that members of different racial groups commit crimes at different rates — they are “immediately infected with both the feeling of outrage that these truths are unsayable” and are provided with “no defense against taking them to what we might consider to be rather repellent conclusions.”

That’s unfortunate, Mr. Pinker argues, because while someone might use these facts to support bigoted views, that needn’t be the case, because “for each one of these facts, there are very powerful counterarguments for why they don’t license racism and sexism and anarcho-capitalism and so on.”

He then goes on to carefully explain those counterarguments: For example, while at the moment it’s true that, according to the Bureau of Justice Statistics, the homicide rate is higher for blacks than for whites, that doesn’t really tell us anything about a group of people since at different times in history, different groups have had elevated crime rates — at one point Irish-Americans did. By that same token, he says, “the majority of domestic terrorism is committed by right-wing extremist groups,” not Muslims.

It would be impossible for a reasonable person to watch the eight-minute video and come away thinking Mr. Pinker’s point is to praise the alt-right rather than to make a psychological argument about political correctness, alt-right recruitment and how to better fight that movement’s bigoted ideas

Now, maybe you disagree with certain parts of this argument — I do, in that I think Mr. Pinker overstates the intensity of campus political correctness — but it’s hard to have that debate in the first place when such a wildly skewed version of Mr. Pinker’s point is spreading like wildfire on the internet.

Steven Pinker will be O.K. A fleeting Twitter blowup isn’t going to bruise his long and successful career as a public intellectual. But this is happening more and more — and in many cases to people who don’t have the standing and reputation he does.

It’s getting harder and harder to talk about anything controversial online without every single utterance of an opinion immediately being caricatured by opportunistic outrage-mongers, at which point everyone, afraid to be caught exposed in the skirmish that’s about to break out, rushes for the safety of their ideological battlements, where they can safely scream out their righteousness in unison. In this case: “Steven Pinker said the alt-right is good! But the alt-right is bad! We must defend this principle!”

This is making us dumber.