I think it is worth discussing what kinds of things can and cannot be displayed. Firstly I think that freedom of speech has nothing to do with the issue, and I feel it is important not to throw around big concepts like freedom too lightly. This cheapens them, especially in cases that one does, actually have to fight for them. AT is a private site that decides on its own which content to display. It is, however, not obligated to display all content. The deck's publishing is not being stopped and its dissemination isn't being impeded. Freedom of speech is about those things, not the choice of an individual to engage or not in certain material. I am not censoring Kim Kardashian by refusing to share on Facebook any story about her (nor do I feel the need to). It is simply my choice not to engage with that.
That being said, not all censorship is bad, and it is often the progressive choice.
Some things are offensive like hate speech, racism and the like. Let's say there actually was a Nazi deck, and not one that tried to show their "good" sides. An actual deck filled with Nazi slogans, Jews as the Devil, all the familiar caricatures, the works. Such a deck would almost certainly not be displayed as that constitutes something who's mere display is an offence, is damaging and is also illegal in many places. A deck filled with racist propaganda would probably not even register on the radar of most of the Tarot community, as it would be "self-censored;" that is, sites like AT would refuse to list it.
However, the Cultural Revolution Tarot does not fit this criteria. It is offensive in my eyes, but that does not make it objectively so. It does not include deliberately racist images, it does not have an agenda that would disqualify it as a "real" deck. It does not seem to have inappropriate nudity or bestiality or pedophilia.
In truth, it does not have any qualities about it that would deem it worthy of a ban. It is in highly bad taste, true, but that's all. There is nothing to ban.