It's always been about social class. Race just happens to be a convenient justification, because there's a visible difference. It keeps scared, gullible people from realizing what it's really about and rising up against their oppressors.
When I was living in Vermont a book called Breeding Better Vermonters was released about the eugenics programs in that state in the 1930s, but they were in other states too. In Vermont, much of it was against the Abenaki people. They protected themselves by blending. Then when it was safe to seek tribal recognition, they had a hard time doing the paper chase, but finally succeeded.
Now, the eugenics movement targets disabilities. Trisomy 21 and other syndromes that have genetic markers have been easy targets. Autism Speaks proudly funneled a lot of money and scouted good researchers to find a genetic marker for autism, but has been unsuccessful so far. It is my understanding that they have backed off, but I am not part of the inner circle.