Kind of silly of you to say this since by virtue of being here you, too, have accepted this since Reddit can also censor you.

As a subreddit moderator myself, I technically censor people every day when I remove posts that don't comport with the rules of the sub I moderate.

At any rate, it's self-imposed, as you said, meaning it was a choice the person made. That has nothing to do with you. There's nothing wrong with a person having the choice and deciding the pros outweigh the cons.

As for being on guard about the government taking away your speech, but not private entities, that's by design. The First Amendment only protects your freedom of speech in so far as government encroachment is concerned, and that too has limits.