In 1900, most people would have been aghast at the thought of permissive divorce laws or form revealing clothing on women. In 1950, these areas would have been more acceptable, but most people would have rejected casual sex and abortion on demand. Yes, and they would have been absolutely apoplectic about the notion of some n****r marrying a white woman.
If you're going to discuss the merits of constraints based on public opinion, and/or of laws written to enforce those contraints, you have to deal with the whole package.
Some early advocates of sexual freedom were themselves white supremacists. Margaret Sanger, the early 20th Century birth control crusade, was an advocate of eugenics. She believed that nonwhites, along with whites from southern Europe, were genetically inferior to whites of northern European extraction. The sex researcher Alfred Kinsey excluded Jews and blacks from his staff.
Racism is far from the exclusive property of holders of traditional values.