Please show me where Adolf Hitler or Charles Darwin, both long dead, have posted on this thread. The linkage of Darwin to Hitler may be wrong, but it is not an ad hominem attack unless you have a definition of ad hominem different from the standard one.
Actually, the linkage of Drawin to Hilter could be correct, but it is still ad hominem -- if the intent is to discredit Dariwn's theory of evolution by that process.
Ad hominem is a fallacy of irrlevance. Its form is to discredit the man. But in actuality, that's irrelevant to the correctness or incorrectness of his theory.
If we assume that Hitler derived all of his evil notions from Darwin, it still doesn't say that the theory of evolution is scientifially in error. The link between Hitler and Darwin would have some historic interest, but no scientific usefulness.