LAST week, I posted a video of an impressive young man delivering a moving short speech in opposition to the attempt to add an amendment to Iowa's constitution outlawing gay marriage. Steven Landsburg, an economist at the University of Rochester, was not impressed.

In a video that's begun to go viral, University of Iowa engineering student Zach Wahls attempts to refute this notion [that gay people, on average, are less successful as parents] without offering a shred of evidence beyond a single cherry-picked case (his own) to prove that children of gay parents sometimes turn out just fine (except, perhaps, for their ability to reason)... What's particularly disturbing to me is all the chatter about how eloquent this kid is, as if eloquence in the service of intellectual misdirection were somehow something to be admired.

There are a number of things one might like to say to Mr Landsburg, but let me congratulate him instead for his inspiring opposition to fallacious arguments from anecdote. One may wonder, however, whether this commonplace error is among our society's most pressing problems, much less among our society's most serious epistemological failings. I take it that Mr Wahls' problem, the problem he was addressing in his uplifting oration, is that a powerful political faction convinced of the essential evil of homosexuality by a magical book seeks to injure his family by voiding his mothers' marriage of its legal standing and stripping his family of the status and respect that flow from that. The science-minded Mr Landsburg may be shocked to learn the assault on marriage equality in Iowa and elsewhere is not predicated upon the modest empirical hypothesis "that gay people, on average, are less successful as parents"; it is based on a conviction of faith that homosexuality is a sinful perversion inherently corrosive to the values that make healthy families possible. Mr Wahls' upstanding, A-student, Eagle-Scout character together with his normatively wholesome family life is sufficient to cast rational doubt on this rather sweeping article of faith.

Let's suppose, though, that there is a credible basis for the proposition "that gay people, on average, are less successful as parents", and that this has something to do with the gay-marriage debate we have been having here in Iowa. What then? Consider an analogy. There is evidence that people in dire poverty are, for a number of reasons, less "successful" as parents. Suppose some of us therefore proposed banning marriages between poor people. The first argument against this proposal is that the right to marry should not depend on membership in a class that is, on average, as successful at parenting as other classes. The second argument is that stripping poor people of the right to marry strips them of legal equality and what John Rawls, the great political philosopher, called "the social bases of self-respect". This harmful injustice would be suffered by the whole class marginalised by official discrimination, but it would be especially salient in the case of exemplary poor families clearly deserving of equal standing, recognition, and social esteem. The moving story of an exceptional family that would be harmed by the proposed codification of inequality draws our attention germanely toward the broader injustice such a law would create. Mr Wahls' primary argument seems to me to be of this sort. Again, this former logic instructor can see no sophistry in it.

Economists like Mr Landsburg specialise in the study of instrumental rationality. To act rationally in this sense is to take the means most conducive to one's ends. Sadly, means-ends rationality and epistemic rationality are often at odds. Fallacious arguments can be the best means to noble ends. If we were to concede, for the sake of argument, that Mr Wahls did fallaciously attempt to rebut a statistical argument with an anecdote, it may remain that he acted not "in the service of intellectual misdirection", but instead acted with exemplary rationality and morality by speaking eloquently in the service of justice. The kind of humanising anecdote Mr Wahls offered does in fact tend to elicit sympathy and weaken ill-founded prejudice. Maybe the relatively tolerant attitude of people with gay friends and family flows from some kind of statistical slip-up, but that's how we are. A rational rhetorician takes his audience's inclinations, rational or not, into account.

In this light, Mr Landsburg's criticism of Mr Wahls' alleged error of reasoning seems to come down to a demand that the young man behave instrumentally irrationally and fight for his moral cause with inappropriate rhetorical means. Does Mr Landsburg believe Mr Wahls' duty to observe the canons of sound reasoning trumps his duty to defend justice and the honour of his family? Maybe Mr Landsburg is hostile to marriage equality and just wants the guy to fail?

Well, I'm pretty familiar with Mr Lansdburg's often illuminating popular writing, and neither of these explanations seems right to me. He's got no problem with gay marriage, as far as I know. And he certainly doesn't think people should undermine their honourable aims by behaving irrationally. So what gives? My guess is that, like a number of right-leaning economists, Mr Landsburg has a regrettable tendency toward tone-deaf, context-dropping, contrarian provocation based on an unexamined assumption that this is what it means to be bravely rational. It is not. In any case, I think we can all agree that, other things equal, intellectual misdirection is not "something to be admired".