Based on what I have heard a journalist say if you are going to moderate and ban content from your platforms different laws apply to you in the US and you become liable for the content that is published. So if Facebook and YouTube want to ban users content they are no longer an open platform like a telephone service and journalistic standards apply, that means everything has to be vetted before it is published, clearly this would send them broke, the alternative is to behave as a platform and wait for the law to tell you to take something down that is illegal, just like when a telephone service is being used illegally
