It is important to distinguish between the scientific concept of law as a generalization, and the social concept of law which is prescriptive and nor… - Mordechai Ben-Ari

Just because people doing science are embedded in a particular social and cultural milieu, it doesn’t follow that science is not universal.

We can define a fact as an observation backed up by such a preponderance of evidence that no useful purpose would be served by doubting it.

Social Darwinism and eugenics are unscientific in two aspects. First, they commit the naturalistic fallacy, which is the assumption that what is, must be. The fact that the natural environment selects for reproductive advantage does not mean that we, as humans, should be forcibly selecting people according to some preconceived notions. The second nonscientific aspect of these movements was their narrow interpretation of the meaning of fitness. In evolution, this simply means fitness to survive and reproduce, not fitness according to some externally imposed criteria.
Darwin himself never engaged in these speculations, nor did he support these perversions of his theory.