Anyone who uses them has effectively elected them, so they probably have more support than any of your political hero's.
Regarding free speech, there is no such thing. Everyone has a line drawn, we just draw them in different places. My question for you is, if you were a server, would you allow content to be posted by Islamic Fundamentalist Extremists? What about violent pornography? Would you let kiddy fiddlers share their experiences?
Assuming your answer is a respectable NO, then I guess you have just voted for yourself to set the boundaries of free speech.
They have just done the same thing. Is there a problem with setting your own terms on your own platform? If the user doesn't like it they can always join different service. That is how free speech really works. You want to say something unpalatable in one venue, go out there and find your listeners in a more friendly venue.
Free speech is not a product of mandatory enforcement. It is an opportunity. In America it is a right, but so is the right to bear arms, and yet I am sure you wouldn't be allowed to walk into many buildings visibly brandishing a gun - is this a breach of rights?