Most of the criticism of Yarvin is by those unable to distinguish between descriptive and normative ideas. His writing is a giant "what if" that mainly rejects the provincial notion that only today's common views are the most sound.

I'd bet that the adjacent commenter's idea of "[his racist advocacy] is well documented" comes from Twitter and Tumblr quotes taken out of context, cyclically retweeted in outrage.

That blacks are ideally suited to being slaves. His advocacy of this is exceedingly well documented.

(You might argue that this isn't technically violence in itself, but it's hard to argue it's not an explicit endorsement of a system of violence.)