Personally I don't think these companies should be legally forced to support freedom of discourse on their platforms by the government.
I think that consumers should force the companies to support free speech, and they should punish companies that support censorship by boycotting those companies into bankruptcy.
The world is a better place when it is free from censorship. Censorship is still bad, even if it is legal and done by private parties. Censorship supporting people and companies should be bankrupted by the market.