Social media above a certain size should be treated as common carriers. There are no reasonable alternatives to them, and today, common public activities activities that are core to our life are conducted on these large platforms. This is not a matter of protecting the freedom of companies to do as they wish - we already regulate companies and restrict their activities in many ways. Private power utilities cannot discriminate against their customers based on their speech or political viewpoints, for example. The same regulations can be enacted to govern these platforms.
I often see arguments saying that someone who is deplatformed/demonetized on these service can just use an alternate service, but I find that to not be the case in practice. Consider that Twitter, Facebook, and YouTube have more users than virtually all nations. Their network effects are core to what the product is, which is why there aren't suitable alternatives (especially when they enact censorship in unison). Telling someone to just go use a different platform is like telling someone that they don't need their power utility, since they can just stick a windmill on their property instead.
Finally, I am greatly concerned that these large privately-controlled platforms are essentially outsourcing government-driven censorship and also violating election laws. For example when conservatives did form their own platform on Parler, AOC called for the Apple and Google app stores to ban Parler after the Jan 6 capitol riot (https://greenwald.substack.com/p/how-silicon-valley-in-a-sho...). If a sitting member of the government pressures private organizations to censor others, it should be considered a violation of the first amendment. Leaving aside the technicalities of law, it is unethical and immoral even otherwise and completely in conflict with classically liberal values. Actions taken by these companies to suppress certain political speech in this manner also amount to a donation to the other side. This isn't recognized as "campaign funding" but it is probably more effective than campaign funding at this point. We need to do a better job of recognizing the gifts-in-kind coming out of Silicon Valley tech companies towards political parties based on the ideas they suppress/amplify/etc.