Finally, giant corporations are deciding what is and isn't true on their global-scale platforms. As epistemology and history teaches us, the means to human progress is cementing the status-quo, via giving a small group of unaccountable, politically/profit-motivated bureaucrats the means for unilateral censorship.

I’m curious if they’re also banning tankies, 9/11 truthers, and violent antifa activists.

Yes.

First, the ban on supremacists will remove Nazis and other extremists who advocate segregation or exclusion based on age, gender, race, religion, sexual orientation, or veteran status. In addition to those categories, YouTube is adding caste, which has significant implications in India, and “well-documented violent events,” such as the Sandy Hook elementary school shooting and 9/11. Users are no longer allowed to post videos saying those events did not happen, YouTube said.

Is the implication of your question that Nazis, Sandy Hook Truthers and Holocaust Deniers are right-wing and so they need to be even handed and ban left-wing groups too?

Not so much that they should be even handed as that they shouldn’t ignore similar bad behaviour just because it does not appear as salient from their perspective.

I think the best outcome is for Youtube to ban anyone who promotes or engages in violence or otherwise hateful behavior, regardless of political views.

Some of the actions of left-wingers on social media recently have become disturbingly extremist and that too needs to be culled for the safety of everyone using these services. As the reach of social media has extended, the notion of actions on these platforms having no real-world consequences is sadly a thing of the past.

This is nothing but a good thing.

Ideally, public naming and shaming should be enough. Unfortunately, unless you get views for calling out bad behavior, doing so can cost you likes. This might have some content creators hesitant to act. A corporation might have more latitude, so maybe they risk the backlash instead.

It's their platform, they can do what they want, but I personally dislike this urge to ban everything the group consensus doesn't like. Leaving aside questions about "which group" and "whose consensus", I don't like it mainly because I've always been the guy in my social circle that is interested in things no one else is. I will watch videos about odd topics because I like to test my base presumptions at times, for example. I went on a flat earth video binge a while back because one friend's wife fell into that rabbit hole. Was there something very basic about my understanding of the world around me that I could be missing somehow? Turns out that, no, there wasn't. Not that I could find through those videos, anyway. Same thing with moon hoax videos.

I don't think I've ever watched a nazi video or a holocaust denial one, but I have watched a Sandy Hook one. It was along the lines of assuming the government, or the Left, or whoever, is trying to manipulate you and see what facts you can find that might fit that model, ignoring anything that doesn't fit well. It was an interesting mental exercise, if nothing else.

At the very least, where will you point people to examples of people slipping off the tracks without realizing how they got there? I'd rather YT hid them behind the equivalent of an adult content flag, if they feel they have to do something, rather than banning them. They will just appear on some other site, which will suddenly become blocked by all the major players, including banks.

Just my opinion, and an admittedly unpopular one.

Obviously Nazis, Holocaust deniers, and Sandy Hook Truthers are bad.

But if you don’t think corporations should decide what we watch or read peertube is a decentralized alternative. https://joinpeertube.org/

What happens when they quietly start banning subjects that aren't as objectively bad?

What you said is called the slippery slope fallacy. Just saying.

It may be a fallacy to assert that it will happen, but it's entirely logical to observe that the current developments make that eventuality more likely.

Slippery slope goes both ways.

What if giving platforms to Sandy Hook Truthers enable them to recruit more and more crazy people, who would do more crazy things than just making videos, for example, actually seeking out victims of Sandy Hook and harassing them?

...Oh wait.

While not a "ban" they already have taken measures against videos/channels that are primarily gun focused.

Slippery slopes are possible, it’s only a fallacy because a slippery slope isn’t a logical proof. Just like an appeal to authority isn’t a proof but can still lend support to an idea.

Is it a fallacy? China has various justifications for their great firewall. Given all the things the US government has done over the years, I can't say I trust them much more...

They'll never do anything like that. They have to keep the masses safe from ideas that could be considered harmful.

So then they ought to shut down? I was gonna say they'd go down to just kids content, but complex ideas can be hidden in that leading to even that potentially being considered harmful by some.