I don't agree with censorship, although that's not blanket as certain things, hate speech being an obvious one, should never be countenanced.
That said, these sites are designed to engage & retain users, allowing you to follow who you want and then presenting back to you like minded content / opinions. Given the various things posted on here, people are not having any difficulty finding people/opinions that they agree with, whether those opinions are accurate or not.
They are also public companies, i.e. the ownership. The leadership & the employees may allegedly be "liberal", but the ownership are the shareholders, who can get rid of the leadership if they don't perform. The company purpose is to deliver value for the shareholders. If policy decisions run counter to that and impact the bottom line, then the leadership will be in trouble.