The "bad actors" that you're referring to on YouTube aren't harassing anyone or inciting violence or breaking the YouTube community guidelines in any way. They are simply espousing opinions that you dislike and disagree with.
Sure, YouTube is allowed to do anything they want. But suppressing an open marketplace of ideas isn't in society's best interests. If unpopular opinions were suppressed in the past, the movements for women's rights and gay rights and civil rights would have faced a massive setback. And let's not even get into the question of whether it's in society's best interests for a handful of corporations to arbitrarily decide how to censor the marketplace of ideas.
I'd like you to take a minute and go visit sites like Voat or Gab. Just, hover around there for a bit if you haven't. Those are sites that are exactly what you want: A pure and open marketplace of ideas without any sort of censorship or rules. This is to prove a point.
Which is that an open marketplace of ideas has no value in itself, because the marketplace can be very easily taken over by bad actors if you don't exert some control over your userbase.
Clearly YouTube has been extremely valuable even before they felt the public pressure to penalize "low quality content".
Your comment about an "open marketplace of ideas having no value in itself" is very curious. The very idea of freedom of speech being a good thing is predicated on the idea that an open marketplace of ideas is a good thing. If it isn't, you may as well lobby the government to ban any and all speech which you consider corrosive.
"When men have realized that time has upset many fighting faiths, they may come to believe even more than they believe the very foundations of their own conduct that the ultimate good desired is better reached by free trade in ideas--that the best test of truth is the power of the thought to get itself accepted in the competition of the market, and that truth is the only ground upon which their wishes can be carried out. That, at any rate, is the theory of our Constitution. It is an experiment, as all life is an experiment."
Did you actually visit Gab or Voat? I'm asking you this because if you haven't, then you can't actually argue in favor of the 'marketplace of ideas' very well. Either that or you're not willing to argue in the defense of such sites. Or you're possibly being disingenuous, considering we've switched from corporate curation/censorship of their content towards government censorship which are two very different topics.
As I mentioned, places with zero censorship and zero moderation can and are very quickly overtaken by malicious actors. Either way, if you're willing to defend Gab and Voat on their merits of being an 'open marketplace of ideas' after having gone there then we can continue our argument.
Sure, YouTube is allowed to do anything they want. But suppressing an open marketplace of ideas isn't in society's best interests. If unpopular opinions were suppressed in the past, the movements for women's rights and gay rights and civil rights would have faced a massive setback. And let's not even get into the question of whether it's in society's best interests for a handful of corporations to arbitrarily decide how to censor the marketplace of ideas.