I fully support the rights of private companies to do that.
People are also entitled to be critical of such moves and to look for alternatives. That's all.
What if Google would openly support fascism. Would you also defend their right to do so, because they are a private company? Would you happily continue to use their products? Or would you prefer to have an alternative?
What is universal free speech except a desire to have the government dictate what companies can have on their platform?
If Google supported fascism, yes, I would want an alternative. I wouldn't support them.
I would sell my phone. I wouldn't be surprised if they started removing apps that didn't conform to their ideology.
But here's the thing. This social network does not moderate people posting about killing their political enemies.
I would not defend your hypothetical Google's right to support a hateful ideology.
Edit: with "universal free speech" I just mean it has to be legal to say things. I am not generally in favor of regulating companies. At the moment they are mostly regulated to censor stuff, though. While I think it also agrees with their own ideology (see Zuckerberg's personal statement), governments have also threatened the social networks if they don't cenor according to the wishes of the governments. (I know about the hate speech laws in Germany, not sure what is the current state of affair in the US).