This is an interesting question; what is the relevance of the DSM? To most people it has none. I don't see that you have persuasively supported your supposed argument, that the humanist's support for egalitarianism is superficial. Manifestoes from humanist societies speak only for the authors of those manifestoes, just as the authors of the DSM speak only for clinical psychologists/psychiatrists. Those authors have decided they were wrong in the past, in all likelihood they will do so in the future. In no case do their attempts at understanding psychological health or illness constrain or define the mental health of the broader public.

Your strawman is assigning beliefs or values to a broad swath of people, humanists, white men, or whomever, and then criticizing those presumed beliefs or values.

You don't really know whether "the humanist's support for egalitarianism is only superficial", you don't speak for all humanists, the manifestoes you cite don't speak for all humanists, and it's a near certainty that most people who accept some of the values that could be called humanist disagree with many others who also accept some.

"White men" are no more a homogeneous group than are humanists, or religionists, or non-white people, and assigning values, beliefs, or attitudes to them as a group is either ignorant or dishonest;)