It is a moderator's right to have controls upon their subreddit to promote good function and well being of the subreddit. This is comparable to the role of any regulator of any institution. It is not censorship to promote a decent subreddit culture in accordance with the standards of a subreddit, otherwise banning spammers would be considered censorship as well. It's one of those 'free speech has its limits' deals you see in any liberal governing body. If you would argue that the libertarian ideal that downvotes are sufficient at accomplishing this task, that assumes that the majority of subreddit knows what is distasteful and denigrating to the integrity of the subreddit, which is defined by the moderation. It's similar to the conception of human rights and constitutional rights in order to defend things proven hurtful to a population from occurring via a faulty directive by the majority. To call this censorship is foolish, as it does not devalue your free speech in the realm of freedom of expression in accordance with the liberal principle of 'live and let live'. This action, taken by one PerpetualDick is the true devaluer of free speech, as it denigrates minority voices.

EDIT: As an addition, I see you posting around this issue that you are an asian person. To be frank, just because you are asian it does not make you an arbiter of what asian people are offended by (there was another post in protest, I believe, and their voice can't be triumphed over via that method, showing a division (racialized people are not a homogenous voice, obv)); not to say that being a POC means you don't have stronger weight on the issue but it's a matter of relevance. It is not speaking to your particular experiences as a POC, but rather an opinion informed by more generalized experience (you are speaking to a more generalized idea of free speech, a political conception considerably seperate from the subject matter at hand), which strikes me as irrelevant to the characterization of your opinion. If I misunderstand, please correct me.