There might actually be a principled argument for social media companies banning all elected officials from posting/tweeting, on the argument that spending time instantaneously communicating with the public is a distraction from the business of governance. Of course, as social media companies are private enterprises, it should be up to their shareholders, and (alas) would be up to their management, to decide whether the public good from getting elected officials out of the public spotlight would be worth the hit to their bottom line such a policy would generate.