I wouldn’t call muting users censorship at all because it’s an individual decision. The muted user still gets to distribute their content and the people who want it still get to view it; there’s no central authority blacking things out wholesale or deplatforming anyone. Muting is no different than turning off the TV or putting down a magazine when you decide it’s not something you want to see.
A no-porn relay would be great (I’m really surprised it doesn’t seem to exist now, but I’m a noob so maybe I’m missing it), but unless no-porn relays are the only ones you’re in, you’re still probably going to encounter it. Here’s hoping several get built soon enough to build a large base and have a good network effect.