Both people's rights actually. I agree they are wrong, stupid, and unhealthy for all people involved but it is a form of freedom of expression providing everything is consensual. Same thing with hate speech, it is wrong stupid and immoral. But if you value freedom of speech, you basically have to acknowledge people have the right to say things you don't agree with or just abandon the concept of freedom of speech altogether. Its now only freedom of speech for people that agree with you, which isnt really freedom of speech.
No society that has tried very strict definitions of what you can and can't do ever turned out well. This is how you get your Stalins, Hitlers, Maos, etc. Even freedom of religion. We all know Christ is the way, the Truth, and the life......but if you also support freedom of religion and the right for people to choose their own religious beliefs, you have to also acknowledge that a satanist has the right to be a satanist if they choose or you don't really believe in Freedom of Religion at all. It doesn't mean you agree with or condone the choices a person makes, its just a matter of if you believe people have right to make their own choices regarding religion or not.