Critics are using bad arguments against a bad candidate

But there’s also the reverse version, in which a policy you dislike does everything bad: It’s inflationary! It’s contractionary! It causes acne!

When you read Veg-o-Matic claims, you should always be suspicious. Sometimes a policy does kill two or more birds with one stone - for instance, there’s a very good case to be made that infrastructure investment under current conditions would create jobs, enhance long-term growth and even improve fiscal prospects. But conclusions like that shouldn’t be accepted without a lot of hard thinking and self-criticism - you need to bend over backward to avoid falling into wishful thinking.

That consideration in itself should have flashed warning signs about, to take one important example, the embrace by Very Serious People of the doctrine of expansionary austerity. It was all too obvious that austerians wanted a reason to cut government spending, and they should have been extremely wary of studies purporting to show that doing so would actually create jobs in a depressed economy. The fact that they instead seized on those studies was a dreadful sign.

In modern America, Veg-o-Matic economics has tended to be a right-wing thing, for a couple of reasons. One is that if your party’s central mission is to comfort the comfortable and afflict the afflicted, you need to claim that all kinds of wonderful side effects will take place from what might otherwise look like a combination of greed and cruelty.

Another is that the parties are different. The monolithic G.O.P. has, until now, been able to get all of its followers to declare that we’re at war with Eurasia, or Eastasia, with no awkward challenges from independent-minded wonks. The Democrats are a coalition in which the wonks have a fair bit of autonomy, and at least believe that they have a professional ethos to uphold.

That said, the Veg-o-Matic temptation exists for everyone. Yes, we see some of it in the populist uprising within the Democratic Party, where anyone questioning the happy talk can be dismissed as a corrupt tool of the corporations. But the big example of Veg-o-Matic reasoning I see right now - in this case the reverse version - can be found in what we might call the mainstream critique of the Republican presidential candidate Donald Trump.

I come here not to praise Mr. Trump - God, no - and would be happy to see his political ambitions buried, with maximum ignominy. He would destroy American civil society; destroy our hopes of containing climate change; and destroy American influence by trying to bully everyone in sight. It’s very scary that there’s any chance that he might end up with his finger on the button.

But too many anti-Trump critics seem to have settled on one critique that happens not to be right: that a turn to protectionism would cause vast job losses. Sorry, that’s just not a claim justified by either theory or history.

Protectionism reduces world exports, but it also reduces world imports, so the effect on overall demand is a wash. Textbook economic models just don’t say what the conventional wisdom is asserting here.

So why focus on such a weak argument against a truly despicable candidate? I think I know the answer: It’s an argument that doesn’t involve taking on terrible aspects of the Trump agenda that differ from the agenda of other Republicans only in degree - as Matt O’Brien at The Washington Post says, on tax policy Mr. Trump is just House Speaker Paul Ryan on steroids.

But bad arguments are bad arguments, even if they are used against a bad guy. And the choice of this argument is telling us something about what’s wrong with a lot of people other than Mr. Trump.