Katherine Stewart doesn’t like Donald Trump’s language about “failing government schools.” School choice, she suggests, has some unsavory ancestors. Libertarianism, for one, “for which all government is big and bad.” And (presumably) even worse: “American slavery, Jim Crow-era segregation, anti-Catholic sentiment and a particular form of Christian fundamentalism.”

One could quibble with some of Stewart’s summation . But it’s certainly fair to note that people opposed to desegregation decided that one way to solve the problem was to get rid of public schools, allowing racists to choose a lily-white educational environment for their children. Maintaining Jim Crow is a vile motive, and it can’t be denied that that was one historical reason some people had for supporting school choice.

Only the proper answer to this is, So what? You cannot stop terrible people from promoting sound ideas for bad reasons. Liberals who think that ad hominem is a sufficient rebuttal to a policy proposal should first stop to consider the role of Hitler’s Germany in spreading national health insurance programs to the countries they invaded. If you think “But Hitler” does not really constitute a useful argument about universal health coverage, then you should probably not resort to “But Jim Crow” in a disagreement over school funding.

Nor is it accurate, or useful, to imply that critics of failing “government schools” today are the direct descendants of those groups, who “really mean” that they want shelter for a racist and anti-gay agenda. No doubt there are people out there who want school choice for just this reason, just as some people out there want a national health program because it will be a more efficient way to implement their eugenics program. After 15 years of writing on the internet, I can guarantee you this: In a country of more than 300 million, at any given moment someone will be saying whatever appalling things you can imagine, and quite a few you couldn’t. Many of them will have taken the trouble to write down and publish their musings, at which point their ideological opponents will pounce to declare that this is obviously the secret key to the thinking of anyone who ever agreed with the author about anything.

None of these super-secret keys has ever opened the door to deeper understanding about anything except the mind of the person waving them. And Stewart’s plaint about the school choice movement is no exception. For many critics of failing government schools, myself among them, have drawn their support for school choice from quite a different source: failing government schools. Some of us actually attended those schools, and were fortunate enough to have parents with enough social or financial capital to get them out when the school broke down.

As we see it, members of the middle class in this country already enjoy quite a lot of school choice; if their local school is awful, they either send their kids to private school, or move. This allows nice liberal parents to proclaim their support for the democratic ideal of a common, public education, while sticking their own kids in an exclusive school. That school may be nominally “public,” but it comes bundled with granite countertops.

We think granite countertops have limited educational value, and are probably best left out of the cost of schooling. And that the extreme residential segregation of this system adds large social costs that go even beyond the gross inequity in educational outcomes.

Meanwhile, we look at the schools those parents left behind: at bureaucracy-crusted institutions that can’t teach kids to read, or graduate them. We know that changing a failing institutional culture is hard-to-impossible, which is why so many foundering companies cannot be saved. Call this market fundamentalism, if you like, but it seems to us that sometimes the only solution for a failing institution of any type is for a competitor to put it out of business, or at least force it to up its game. And when we look at decade upon decade of attempts to reform these particular institutions, we see that history seems intent on proving us right.

Time after time, more money was poured into schools, but produced little in the way of better results for anyone who didn’t happen to be employed by the school district. Time after time, when deeper institutional change was tried, the bureaucracies beat back the reformers. Failing teachers kept collecting their paychecks, and failing students ended up out on the street with no useful skills.

We would like every kid in America to have the same kind of options we did to exit those failing institutions. And while we hate segregation, it’s hard for us to see how vouchers could make educational segregation worse today, given how extreme it already is in most major cities.

Are we wrong that vouchers are the answer? Quite possibly. Certainly vouchers have not proven to be as splendid as we reformers hoped before they had been tried (an epitaph that could be written for virtually every government program in history). Parents like vouchers, and they often save a little money, but vouchers simply haven’t delivered the hoped-for educational improvements. Improvements may come as the market matures. But it’s also quite possible that they never will.

However, that’s an empirical argument not advanced by dark insinuations about the motives of those making it, whether it’s calling those favoring vouchers neo-segregationist Bible-thumpers, or tarring those opposed as anti-Christian bigots and hapless tools of nest-feathering educational unions.

Ad hominem is always a game that both sides can play with equal success—and one in which everyone ultimately loses. That’s not the kind of game we should play with the education of our children.

This column does not necessarily reflect the opinion of the editorial board or Bloomberg LP and its owners.

Megan McArdle is a Bloomberg View columnist. She wrote for the Daily Beast, Newsweek, the Atlantic and the Economist and founded the blog Asymmetrical Information. She is the author of “The Up Side of Down: Why Failing Well Is the Key to Success.”

1. For example, it seems odd to lump the Catholic Church in with the victims of school choice. The late-19-century Blaine Amendment seeking to forbid the use of tax money to fund religious schools was essentially an anti-choice program, aimed at a Catholic education movement that predated the Republic, and extended well beyond its borders Although the amendment failed at the federal level, many states incorporated some version of it into their state constitutions. I can’t imagine how you square this with the notion that school choice fundamentally has its roots in the Know-Nothings.