So can twitter ban me from using their services or viewing tweets? If we declare twitter the same as a DMV window, it greatly complicates the public/private division.

And what if Trump abandons twitter and decides to join chirper (I made that up, no relationship with anything that might have that name) which is just like twitter but invite only and has an open policy of banning liberals (which a private company is allowed to do), then what does this ruling mean? Does it mean that no government official can make use of any private company that has any level of discrimination against certain users (and by this I mean a legal discrimination, not based on protected class)? What about Trump joining a private club that doesn't let everyone be members?