Well, I believe you that there are lots of kids there that try to seem racist for 4chan cred, and I guess people would know not to post videos of themselves doing those illegal things.
But I remember they had stuff like "n*gger chimpout" compilation threads, and whenever people talk about what they blame on Jews, they seem to be actually bitter and angry, so they do seem legitimately racist. I wouldn't be surprised if there was a lot of overlap with the people who do commit those acts of violence you're talking about, but even if not, I don't think you could say they're not real racists just because they don't post videos of themselves committing violent hate crimes. The board is just diluted by low-effort threads and bait by users of other boards.
