Barton Swaim is the author of "The Speechwriter: A Brief Education in Politics" and a contributing columnist at The Washington Post.

Then-Republican presidential nominee Donald Trump and Democratic presidential nominee Hillary Clinton debate in October. (John Locher/Associated Press)

When you’re 3 or 4 years old, you learn to draw comparisons. This is like that. Those are not like these. It’s a natural way of learning, and it applies just as much to the adult world of politics as it does to the playroom. You can learn a lot by noticing the differences between candidates and officeholders — rhetorical patterns, ideological premises, loyalties, attitudinal tendencies and so on.

That probably sounds stupidly obvious. But during an election, the stupidly obvious becomes complicated and controversial.

Lately I’ve enjoyed drawing comparisons between otherwise dissimilar politicos, and every time I get the same response. Back in June I wrote a little piece comparing and contrasting the falsehoods uttered by Donald Trump and Hillary Clinton; both, in my view, had a marked habit of intentionally misleading, but in very different ways and for different reasons. A little later I wrote something suggesting that Trump and Barack Obama, for all their obvious differences, both tend to underestimate the competence of their adversaries. In another piece I contended that the effects of (actual) fake news and those of genuine news stories with substantial misstatements and misinterpretations can be similarly adverse.

And last week in The Post I tried to draw out the similarities between Trump’s inaugural address and Obama’s of 2009. Clearly these are very different men with very different aims — is that even necessary to say? — but surely it’s at least mildly interesting that both these addresses exhibited some common tendencies.

After all of these pieces, I was subjected to a barrage of tweets and emails and blog posts and letters to the editor accusing me of perpetrating “false equivalence.” This despite the fact that in each instance I’d gone out of my way not to equate the two sides of the comparison.

And it wasn’t just me. During the 2016 presidential election, the New York Times was so frequently criticized for engaging in false equivalence — “false balance,” as it’s often called in journalistic contexts — that the paper’s public editor, Liz Spayd, wrote a lengthy column defending its coverage of both candidates. The criticism was that, simply by covering the investigation into Clinton’s use of a private email server and accusations that she had used her State Department office to direct funds to her foundation, the Times “equated” her failings and misdeeds with those of Trump. (Were her failings less serious than Trump’s? A lot of people didn’t think so — note the election results — but evidently most of the Times’s readers did.)

“False equivalence” is the presentation of two things as if they’re the same, usually in some nonliteral sense, when in fact they are quite different. A half-century ago you often heard it applied (sometimes with the semi-synonymous term “moral equivalence”) to American reactionaries who claimed the United States was no better than the Soviet Union because both oppressed and censored political dissidents. That criticism was apt, I think, since those against whom it was leveled were not comparing but equating.

Now, however, the term is used mainly — at least in politics — as a stick with which to beat anyone who implies, or even hints at implying, that one person or phenomenon might share certain qualities with another. Suggest that two political adversaries aren’t as different as everyone’s assuming, and prepare for an army of mostly anonymous Twitter users calling you a moron for engaging in — fancy term — false equivalence. (You hope these faultfinders never encounter poetry. “Shall I compare thee to a summer’s day?” No you shall not! False equivalence! “Thy soul was like a Star, and dwelt apart.” A soul is nothing like a star, you idiot. False equivalence!)

Take away the politics, though — take away the desperate emotions of a high-stakes election — and people are quite happy to reflect on similarities without panicking. Consider: If I had compared Clinton’s dishonesty with Trump’s back in 2012, let’s say, before either one had announced as a presidential candidate for the 2016 election, the response would have been far different. Assuming I could have come up with a plausible reason for drawing such a comparison, very few people would have accused me of false equivalence. In 2016, by contrast, we were at war with each other over the respective merits and demerits of these same two people. Many people on the left felt that to talk at all about Clinton’s dishonesty was in essence to praise Trump as a man of rock-solid virtue; and many on the right felt that any talk about Trump’s sketchy business dealings or outrageous remarks was by implication an argument for Clinton’s high ethical standards. No matter what you said about one or the other, even if it was indisputably true, someone was there waiting to thrash you with the false-equivalence stick.

Of course, it wasn’t false equivalence, because it wasn’t equivalence. It was an ordinary pattern of thought called comparison. You learned how to do it when you were 3 or 4. But in an election year, ordinary thoughts get you in trouble.