How so? It’s the same as free speech: the government won’t step in, but it’s still possible to say something immoral

I disagree with him but I don't think those are contradictory. A watered down example: I don't like hot dogs in my macaroni, but I respect other people's right to have them. If you ask me if I want them I'll say no, but I won't tell you not to.
A more ethics one than preference: I think it's wrong to cheat on a romantic partner. It's a bad thing to do and people shouldn't do it. However, I would staunchly oppose a law that said people couldn't. People should have the freedom to do the wrong thing as suits them (boundaries and edge cases not withstanding).

People respecting that other people may have opposing beliefs about how to act and respecting that is what we want, not homogeneous beliefs.

Please do explain how.