The YouTube Rabbit Hole Is Nuanced

  But wait, you used the word free?
  How is paid propaganda free? 
  The way astroturf is grass?

Just asking questions.

Given that applies to about 0% of beliefs for most people, I'd say the idea has some flaws.

If you immediately reject that, you're not very open to external ideas, are you?

If you don't immediately reject it, you see how a market can be subverted to serve purposes that it was never intended to or constructed to resist.

Either way, the idea of a marketplace of ideas is paradoxical in the extremes. And once you acknowledge the idea needs to be softened to avoid self-contradiction, you end up back at the question of what constitutes abuse. That's the exact same question people are wrestling with now. And because it's inherently an expression of a power struggle, you need to be aware of whose power you're supporting.

I recommend siding against authoritarians and fascists, but that's just my idea.

Second, even if ideas are treated as a market, movements can have disproportionate power compared to their "market share". The level of group support required to implement a policy depends on the specific policy. If 5% of people support defecating in the local lake, and 95% of people support the idea of swimming in the lake and using indoor plumbing, the result is not a swimmable lake. In the same way, a violent movement with very low popular support is unlikely to win any elections, but can still make it entirely unsafe for that movement's targets.

Third, personal anecdote time. A few years ago after watching the "Alt-Right Playbook" [0], a YouTube series about recruitment and radicalization tactics used by the alt-right, YouTube recommended that I watch Nazi propaganda. I do not say that in any exaggeration. The video title had the phrase "The Jewish Question", and I was expecting a history on how that phrase had been used in racist fearmongering. It was instead exactly that same racist fearmongering. Even if I were to hold that all speech is permissible without repercussion, there is still a world of difference between allowing Nazi propaganda to exist, and active promotion of propaganda of that same propaganda.

TL;DR: Ideas are not a marketplace, and lack of promotion is not the same as silencing.

[0] https://www.youtube.com/playlist?list=PLJA_jUddXvY7v0VkYRbAN...

Or lets ask differently: how could there ever be a neutral layout to said market place, which is without influence of the powers at play in any given situation?

Megalomaniacs shouldn't be involved in potential nuclear war. The US has proposed structured human-in-the-loop treaties to require that nuclear weapons not be automated, but China and Russia have both refused. A few bad cosmic bit flips and unintended nuclear war is possible. Putin's swan dive into Ukraine should underline the need for change. Humanity is toast if we're going to play stupid nuclear brinksmanship games every couple decades.