For a site like Youtube they shouldn't be able to discriminate against free legal speech because they have captured too much of public discourse and information dissemination to give them that power over us.

Nobody is forced to use Youtube. They haven't captured public discourse, people choose use their services. If you don't like what they're doing, don't use it. Youtube doesn't control how I use my first amendment rights, because I don't use Youtube (or at least, I don't have an account there). There are better, decentralized, and more open alternatives to Youtube and other social media and if you choose not to use them it's on you.

Not sure if you don't believe in any regulation on private business or not. A few questions. Do you think it would be acceptable for telecoms to kick people off or disallow them service because they are known to be conservative or liberal? Imagine not being able to call someone because they're a conservative or liberal. How about Verizon and Comcast not giving you service because of that, so no broadband internet. Would you be okay with ISPs blocking any sites they want including proxies and VPNs? Would you be okay with pharmacies and drug companies denying people their service and products for their political affiliation or views? How about grocery stores? What about a restaurant denying service to people because they're Muslim or black or white?

I only believe in regulation of private businesses if they're violating someone's rights. This means polluting the environment, physically harming someone without provocation, stealing someone's property, that kind of thing. The telecoms industry is a unique bag of worms, because it's a government created monopoly which is not good. In a free market, yeah ISPs should be allowed to deny service to anyone, block sites/VPNs, deny service to anyone. This would be a shitty thing to do though, and people would rightfully boycott their services. Same thing with other industries...people do ban people from their businesses for racial, religious, or other reasons and they rightfully get called out and boycotted for it.

I think you maybe misunderstood, ruling a site like Youtube as a legal public forum would mean they have to allow free legal speech and not discriminate at their choosing with all their political biases. The government would only get involved if they weren't allowing free speech.

This is a nice ideal, but you're expecting the same government (I assume we're talking about the US government) who persecutes whistleblowers, spies on it's own citizens, spreads propaganda, interferes in foreign elections, props up dictators and rebels then turns on them the next week, wants to ban encryption, I could go on and on... we're just going to give them the absolute authority to enforce "free speech" and prevent discrimination online. I don't think so. Absolute power corrupts absolutely, and the US government is already a behemoth far outside the constraints designed by the founding fathers.