This list makes me sad.

If anything, not being able / advised to discuss any of the above topics reflects significantly less rationality than the average person, perhaps somewhere between children and autists. Why? Just why? What point is there in putting a moratorium on such a big chunk of human experience (many of them are admittedly not the best and brightest, and I'm not saying I'd suddenly like LW to be filled with nothing but that, but adults should be able to handle them), all the while getting absurdly fretful about acausal cosmic horrors that fail to show any plausibility to most smart and reasonable outsiders?

... If I tried, the best thing I could say about a crowd that would abide by such norms is that they have a highly lopsided intellectual development. A more biased but likely proposition would be that the failure to handle banal conversation topics like pop culture or humour casts doubt on the truth or intellectual value of the things such a crowd does accept to discuss, and professes expertise about.

Edit: if in the context of topic recommendations for a top-level post, such as an entire post being a joke played at the expense of the community, then yes, this might make sense -- but instead of an oddly specific list, you could have said simply "disruptive topics", topics that make the audience wonder whether the author is messing with them or simply has no sense of propriety. But if you meant "things that do not have a place on LW in any way, shape, or form", then I stand by the above.