Kind of a long post, here's a TL;DR: I think the real reason Lil' Dicky was banned from HHH was that he draws to much popularity from mainstream reddit and the mods want to keep discussions and votes to the HHH community. I don't think they were right to ban Lil' Dicky posts, but I at least see where they were coming from.

I definitely don't agree with it, but it at least makes sense to me. Everybody's saying that it's because he mocks the genre, but while that has something to do I don't think it's the real reason (I also personally don't think that's true).

Basically Lil' Dicky appeals to the vast majority of the reddit community, it's basically his target demographic and he does an excellent job of making music for them. Because of this any type of Lil' Dicky post will draw a lot of attention from a lot of redditors.

Not all subreddits, but a lot, and certainly HHH try to separate themselves from the main reddit demographic, I think this basically comes down to wanting to avoid the reddit hive mind and have discussions from people who are actually a part of the community and share similar values to everyone else in that subreddit.

So, whereas in HHH opinions are split on Lil' Dicky, on reddit as a whole he's extremely popular, so any Lil' Dicky post on HHH runs the risk of drawing in the larger community with opinions and votes that don't match the values in HHH. They also run the risk of people going to HHH only for Lil' Dicky, which would skew the values even more, and create potential for people from mainstream reddit to look at, vote on, and comment on other posts on HHH. I think the mods are right to want to avoid this, but I don't think it's fair or good for the community to outright ban Lil' Dicky, I'm sure there are other, better ways to avoid the scenarios I described above.

Anyway, that's just my two cents, and while I don't agree with it, I can at least see where they're coming from.