Yes. Censorship is a neutral term.
> If you expect advertising-powered private platforms that host your content pro-bono...
I expect people to let each other say their piece. Content owners and content hosts have a partnership, and the balance of power definitely tips toward Reddit and YouTube at the moment.
We can argue that "someone can go start up a more permissive platform", but if we're not sharp and clear about how current hosts should behave, the next hosts won't have a clear understanding of what they should be doing differently. If we're not sharp and clear about how current hosts should behave, regulators trying to get YouTube and Reddit out of the moderation business will likely defer to whichever lobbyists happen to be in the room.
I expect that, as always in these situations, a minority of users will migrate to alternative websites (voat, alternative video streaming websites etc...) many of them will end up coming back to Youtube/Reddit because that's where all the content is and the network effect is strong. Repeat in one year when Reddit decides to issue a new wave of subreddit bans. I genuinely don't know how we can get out of this situation.
Or where exactly is the line?
This is not censorship.
I suppose you can say that but I don't think it's a useful definition. Censorship is a strong word, if we overuse it it's going to lose its meaning. Censorship generally has the intent of removing something from society at large because the elites deem it dangerous. Youtube isn't calling for the removal of gun content from the internet, they're just policing their platform. I mean, if what they're doing is censorship then what isn't? HN will ban/flag/delete many off-topic/controversial posts on sight, is that censorship? If your Dungeon and Dragon forum bans you because you posted porn, are they censoring you?
I'm not saying that Youtube couldn't or shouldn't be criticized for their move, I was specifically replying to the parent's claim that there was a change of mentality on the internet at large. Moderation or "censorship" as you like to call it has always existed everywhere, online and off. The real problem here is that Youtube wields a disproportionate amount of power by virtue of being quasi-monopolistic.
If you expect advertising-powered private platforms that host your content pro-bono to suddenly start fighting for your ideals against what they feel is their own economic interest I'm afraid you're going to be disappointed. Especially if said platform has no serious competitors and knows a huge amount of its users is effectively "captive" audience.