Well of course having immoral rules in a private club can be legal. But plenty of wrong things are legal. Every policy I protested in my queer activist life was legal.

Discriminating against transgender people is legal in many circumstances, but it is always morally wrong.

We need to protest this obnoxious campground owner just like we would if he were a member of the KKK or some other equally obnoxious but legal group.

Or just like those private golf clubs that used to refused to admit Black people or women as members. They couldn’t be legally forced to change their policies, because they were private.

But people of good will forced them anyway, by shaming them, withholding advertising, withholding custom, and to a certain extent by ostracizing people who dared join.