It is well established that certain genetic abnormalities result in severe cognitive deficiencies. You can analyse someone's genes, and without knowing anything more about the person than knowing they have three copies of chromosome 21, you can tell they have a severe mental deficiency. Is that dehumanizing? To me, that is just reality, and I think if you view reality as dehumanizing then the concept really is not that meaningful because then it is simply the default state.

Similarly, if I were to believe in astrology, I don't think I could be convinced that it is any more dehumanizing than believing genetics is real.