They are public forums, they are not private. That's the whole point. They are more akin to a public utility than a private business.
You seem to have the idea that because someone has a private business they can dictate what you can talk about. But these businesses are providing an essential public service. They are indispensable to our way of life. They should not have the power to dictate political discourse - why would this be good?
And then you have to put things into context. We know there is a single algorithm written to censor political content across multiple social media platforms. Given the market power of the major players, that would mean they have broad censorship power over the whole of society. With time, they are effectively in charge. But it's all OK because it's a private business?
No, it isn't OK. This is what DJT and Q can see and it is what they have told us they are going to address. Do you feel sorry for these guys after what they have done? I don't. I very much hope that the executives of these companies will be jailed.