As a conservative, you can be confident of two things when you make a slippery slope argument in relation to any left-wing idea or policy. First, that you will be condemned as a paranoid lunatic and promptly laughed out of the room. Second, that you will almost certainly be right. Every week, yet another thing happens in reality that people on the Right, in the not so distant past, warned would happen if we stayed on the current trajectory.
Precedents do matter, which is no surprise to some of us. If something is justified on a certain basis, then everything else that can be justified on the same basis will probably one day occur. If you tear down the statues of Confederate generals because they were racist, then all of the other statues of “racist” historical figures will come down. If you say that marriage is only a consensual contract between people who love each other, then eventually you’ll have