What if Charles Darwin had publicly and systematically denounced racism?

Darwin's theory of natural selection is not intrinsically, or conceptually, very different from ideas of selective breeding that are certainly at least as old as the Neolithic Age, some 10,000 years ago or more, with the conscious and artificial development of the modern cereal grains such as wheat, oats and corn. Effectively, Natural Selection is a notion that favors adaptability and flexibility, with regard to natural conditions, as a means of promoting survival, and indicates that these qualities are passed on through generations of all living organisms. Thus, it would tend to indicate that cross-breeding, and species diversity would, in general be optimal for maximizing the probability of species survival. Effectively then, Natural Selection would tend to argue that racial diversity and interbreeding of races, rather than "racial purity", or inbreeding. would represent the optimal strategies for the survival of the human species. Nevertheless, in "The Descent of Man", Darwin is really rather coy on this subject. He seems to clearly distinguish "savage" from "civilized" races, and implies that Natural Selection can, and should, favor the civilized races, like the British. Now, why exactly did he do this, you ask? And, that is rather a good question. I think the fundamental point here is that scientists are salesmen. The modern scientific method is a very public process, by definition it makes publication and public criticism and discussion a fundamental aspect involved in the evaluation of scientific theory and experimentation. Hence, if views are not popular and marketable with the scientific public, they will not be accepted as "true", whether they are true, or not. Conversely, if scientific publications are indeed popular, they may indeed be accepted as "true", even if they are clearly false by any meaningful objective criterion. Darwin was writing at the period of the peak of British and European Colonialism and Imperialism, it was absolutely fundamental to the government and the economy that control and exploitation of "inferior races" should be rationalized and justified. Hence, there was a tendency for the powers that be to tend to rather simplify the concepts of natural selection to the notion that "We are the fittest, hence we should survive, and everyone else must die!" Now, Charles Darwin could have publicly opposed these views, however, he never really did, to any significant extent, anyway. And, if he had, he might actually have gotten into trouble, because anti-racist views would have been very unpopular indeed in nineteenth century Britain, for obvious practical reasons. Scientists are salesmen, Darwin was a salesman, and a good salesman never intentionally antagonizes someone who is purchasing his products, does he? Probably, Adolf Hitler, was the most extreme exponent of Social Darwinism, holding that racial purity was the only true good, and that all impure, "international races", like the Gypsies and the Jews, had to be exterminated, for the good of mankind. And, he did just that! Adolf Hitler's one true love was his half-niece, Geli Raubal. He wanted to marry her, but, she committed suicide out of pique, when he paid too much attention to Eva Braun. Suppose Hitler does indeed marry Geli, thus maintaining "racial purity", and, because of inbreeding, his children are retarded, hemophiliac etc. Would Hitler have gotten the message, that, maybe the Jews and Gypsies had been right all along? It's quite possible. So, suppose Charles Darwin does his duty, tells the truth, doesn't act like a cynical salesman, and actually denounces, publicly and repeatedly, imperialistic racism as being contrary to sound principles of natural selection? How might this have changed history?