The arbiters of appropriate expression in America get very exercised when conservatives call Barack Obama a “socialist.” They treat the claim in the same way as calling Obama a Muslim, Kenyan, or “the anti-Christ.”

But headlines this week report that President Obama accused the Republicans of “social Darwinism,” and I don’t see anyone exercised about that. A New York Times editorial endorses the attack.

Is “social Darwinist” within some bound of propriety that “socialist” violates? I don’t think so. After all, plenty of people call themselves socialists — not President Obama, to be sure, but estimable figures such as Tony Blair and Sen. Bernie Sanders. Members of the British Labour Party have been known to sing the socialist anthem “The Red Flag” on the floor of Parliament.

But no one calls himself a social Darwinist. Not now, not ever. Not Herbert Spencer. The term is always used to label one’s opponents. In that sense it’s clearly a more abusive term than “socialist,” a term that millions of people have proudly claimed.

The Encyclopedia Britannica says that social Darwinism is

the theory that persons, groups, and races are subject to the same laws of natural selection as Charles Darwin had perceived in plants and animals in nature. According to the theory, which was popular in the late 19th and early 20th centuries, the weak were diminished and their cultures delimited, while the strong grew in power and in cultural influence over the weak.…The poor were the “unfit” and should not be aided; in the struggle for existence, wealth was a sign of success. At the societal level, social Darwinism was used as a philosophical rationalization for imperialist, colonialist, and racist policies, sustaining belief in Anglo-Saxon or Aryan cultural and biological superiority.

Not a pleasant idea. And a pretty nasty thing to accuse someone of. It’s always used as a smear of conservatives and libertarians — by the historian Richard Hofstadter, by the fabulist Robert Reich, and now even by the president of the United States. (Damon Root noted that the real eugenicists were not the laissez-faire advocates that Hofstadter accused but the “Progressive reformers” that he admired.)

As Dan Mitchell pointed out, Paul Ryan’s budget proposes to make the federal government substantially larger than it was under Bill Clinton. Does that make Clinton a social Darwinist?

Those who deploy the charge are, first, falsely implying that Republicans support radically smaller government, which neither Ryan’s budget nor any other Republican plan actually proposes. And second, they are accusing both Republicans and actual supporters of free markets of believing in “the survival of the fittest” and, as Wikipedia puts it, “the ideas of eugenics, scientific racism, imperialism, fascism, Nazism and struggle between national or racial groups.” “Social Darwinism” is nothing more than a nasty smear.

The president should be embarrassed, and those who call for civility in public discourse should admonish him.