There are cases where speech is illegal, even in the USA, which probably has the strictest standards for protecting speech in the world.
Generally though sites aren't responsible for their users' speech, so if someone does cross the line, that would be on the user, not the site. As long as the site responds to any lawful subpoenas, they would stay in the clear.
The US legal system is 100% wholly incapable of keeping up with the pace of internet content for this sort of thing, so embracing the spirit of the laws on speech and applying them within user-content-based-sites is an appropriate minimum.
Even Musk who wanted to turn Twitter into a site dedicated to free speech specifically said he wanted to focus primarily on moderating content based on US laws (something that he has apparently walked back since then since Twitter still aggressively moderates legal content).