Leftists have treated sex this way since there were leftists. For them there is no overriding source of rules and morality. There is not God and there is no god. If there is no God then everything is what you can make of it. There is no reason to live but to get power and money and pleasure. There are no rules limiting the sources of these things. Anything goers and because there is no possible expectation of afterlife there is some desperation in striving for anything that makes one feel good.
The Sexual Revolution