Vetting it would be hard. Most of it is opinion, slander etc. not so much factual. Even the quasi factual content can be spun any which way while remaining within the confines of 'technically correct'.
At what point does freedom of speech qualify the post?
Freedom of speech isn’t a right when it comes to a company deciding what can be posted on their site, right? So they could just have a policy where if they don’t know they don’t let it grow viral. Hell, even a limit of 5000 unique views on all posts probably won’t affect many people until the election is over.