We're not. Stupid things can go make their own websites. Reddit isn't a public service.
I'll start worrying if server hosts were doing this, but if Reddit doesn't want a reputation of "slightly better than 4chan", it should try cleaning up a bit.
Reddit is where you meet people. Reddit has bigger power in directing attention than most advertising networks. Directing attention for private communication is definitely censorship.
I actually think legislation has to be brought up to date here. We seem to favor communicating on privately owned websites, but people still seem to have an expectation of freedom of speech. Law should definitely reflect this common expectation.
I'll start worrying if server hosts were doing this, but if Reddit doesn't want a reputation of "slightly better than 4chan", it should try cleaning up a bit.