I don't have any cogent counterargument. Nevertheless, here's a trifle about the origin of the term social Darwinism suggesting that Kitcher applies the conception that Richard Hofstadter popularised in 1944 through his book Social Darwinism in American Thought (SDAT).
For Kitcher historical accuracy amounts to absolving Charles Darwin and indicting Herbert Spencer as the founder of social Darwinism instead:
“In the interests of historical accuracy, however, it should be clearly recognized that “social Darwinism” has very little to do with the ideas developed by Charles Darwin in “On the Origin of Species.” Social Darwinism emerged as a movement in the late 19th-century, and has had waves of popularity ever since, but its central ideas owe more to the thought of a luminary of that time, Herbert Spencer, whose writings are (to understate) no longer widely read.
Spencer, who coined the phrase “survival of the fittest,” thought about natural selection on a grand scale. Conceiving selection in pre-Darwinian terms — as a ruthless process, “red in tooth and claw” — he viewed human culture and human societies as progressing through fierce competition. Provided that policymakers do not take foolish steps to protect the weak, those people and those human achievements that are fittest — most beautiful, noble, wise, creative, virtuous, and so forth — will succeed in a fierce competition, so that, over time, humanity and its accomplishments will continually improve. Late 19th-century dynastic capitalists, especially the American “robber barons,” found this vision profoundly congenial. Their contemporary successors like it for much the same reasons, just as some adolescents discover an inspiring reinforcement of their self-image in the writings of Ayn Rand.” (Philip Kitcher: The taints of 'Social Darwinism', The New Yok Times Opinionator, April 8, 2012).There are two historical ambiguities included, however. As Matt Young already pointed out at Panda's Thumb, “Nature, red in tooth and claw” is a quote taken from Lord Alfred Tennyson's poem In Memoriam A.H.H.. The poem was a requiem for Arthur Henry Hallam published in 1849 and neither Darwinian nor atheist in its conclusion. Nevertheless, the phrase has a long history of being (mis)quoted by both Darwinians and anti-Darwinians.
The second ambiguity is the now common ascription of social Darwinism to Herbert Spencer, where the laissez-faire opposition to planned state intervention into society and economy is meant in particular. As Thomas C. Leonard of Princeton University concludes, social Darwinism has been established as an epithet for discrediting this free-market philosophy by Richard Hofstadter:
“Hofstadter declared American social Darwinism dead no later than 1918: “as a conscious social philosophy,” Hofstadter said, “social Darwinism had disappeared in America at the end of the war” (1944, p. 175). It is an irony, then, that the term “social Darwinism” gained meaningful currency only with the book that declared the concept long dead. Historians revising Hofstadter have established that both the term “social Darwinism” and the concept of social Darwinism are unexpectedly rare in the 1860–1915 period surveyed by SDAT. [...]
First, Hofstadter in SDAT [Social Darwinism in American Thought] succeeded brilliantly in affixing the epithet “social Darwinism” to free-market economics. His many revisionists notwithstanding, SDAT’s most conspicuous and enduring legacy is its discrediting of Spencer and Sumner with “social Darwinism.” Never mind that neither were especially Darwinist, and never mind that Hofstadter also found Darwinism in reform. In the popular and scholarly mind, Spencer and Sumner are social Darwinism.” (Leonard 2009)Richard Hofstdater, disliking free-market economic philosophies, established the current meaning as an negative epithet of laissez-faire economics. Free markets sounded too positive and laissez-fair too neutral, I guess, so Hofstadter invented a negative epithet for it. By the way, Leonard distinguishes the young Hofstadter from the mature Hofstadter by adding index numbers 1 and 2 to his name. Here, I only dealt with Hofstadter1.
The early use of the term social Darwinism was indeed quite free of negative connotations. In the following, for example, the term occurs in a context that simply cannot be interpreted as having the same meaning as today. It is about the social changes of the landholding system in Ireland and in particular about a (mis-)translation of the original Irish term for lending cattle into English suggesting the lease of land instead. The author disputes this translation as sloppy and then argues that the theory of another author … see for yourself:
“It has appeared necessary to devote some space to this subject, inasmuch as that usually acute writer Sir Henry Maine has accepted the word “tenure” in its modern interpretation, and has built up a theory under which the Irish chief “developed” into a feudal baron. I can find nothing in the Brehon laws to warrant this theory of social Darwinism, and believe further study will show that the Cam Saerrath and the Cain Aigilbic relate solely to what we now call chattels, and did not in any way affect what we now call the freehold, the possession of the land.” (Fisher, Joseph 1877: “The History of Landholding in Ireland” Transactions of the Royal Historical Society (London) V: 250, p. 25)As you can see the currency of the term “social Darwinism” is simply what we’d today call social evolution without any bad implications like “harsh policy”. The author just disputes that the Irish chief “socially evolved” into a feudal Baron - or rather that the Brehon laws can be used as evidence for that theory.
P.S.: Is this a case of an Alma Mater nourishing both Barak Obama, graduate of Columbia University, and Philip Kitcher, Professor of Philosophy at Columbia University, with an understanding of what social Darwinism means derived from Richard Hofstadter1, former Professor of American History at Columbia University?
Update [02.05.2012]: Thinking of it, 'social' is unlikely to be the negative epithet in the term 'social Darwinism', because it usually carries quite positive connotations as in 'social fellow'. That leaves 'Darwinism' as the negative epithet despite being the noun. This seems to make sense, since changing 'social liberalism' into 'social Darwinism' clearly changes the connotation from positive to negative.