This should be an easy one for Gorsuch, the government has no right to forbid private “discrimination” against anyone.
This is a very slippery slope. If the SC finds current laws banning discrimination based on sex also include “gender identity” they will rue the day. It won’t be a week before a white male sues for racial discrimination based on his “racial identity” as a black woman. Soon enough, nearly everybody turned down for a job or fired will be making similar claims.
In the most true Constitutional sense you are absolutely right, but with the passage of the 1960s civil rights laws (which Goldwater opposed mostly on grounds like you would) the concepts morphed in the legal minds from the Constitutional sense that THE GOVERNMENT CANNOT discriminate, to the unconstitutional sense that YOU cannot discriminate. Contrary to the Constitution you became an agent of government policy in your own personal life and own free personal associations. Your freedom became discriminated against by government policy. It is no accident that it was Leftists in the legal profession from which the ideas behind these changes took place.