If your political view you want to promote is so extreme that no company wants to do business with you, although they legally could and you offer good money, then, yes, probably you have to build your own TelCo or Internet or whatever.

Also note: YouTube is already a heavily moderated platform, see pornography.

Followed by "No censorship. You are still free to establish your extreme political views in another country."

Unless otherwise regulated, yes, of course. No one should be forced to conduct business with another party.

Do you have some good reason why we should not change the regulations so that they are "otherwise regulated"? No one is claiming they are currently breaking the law by refusing to conduct business with e.g. gab or the daily stormer or whoever else.

"This should not be illegal because it isn't." is a surprisingly common argument.

In the US, allowing Free Speech on your property is distinct from conducting business on your property. Going by that logic, you can demonetize them, but you can't necessarily deplatform them.