[Zak]

Safe harbor laws make it generally legal for a platform to host such content until certain notification provisions are met. There's a specific process for handling child porn in the US, which you can easily find if you want that in your search history.

Advocating violence against specific people is not illegal in the US unless it is likely to produce imminent lawless action. Saying "[racial slur] should be exterminated" doesn't rise to that standard. A live video saying "everybody get your guns and meet me at [location] - we're gonna slaughter those [racial slur]" probably does, but would be subject to safe harbor protections for the platform.

Libel also falls under safe harbor. The platform could eventually be ordered by a court to remove the content, but not until many people have had the opportunity to see it.