Building on what others have said, online is no different from anywhere else, and all online spaces, left to their own devices, will be overwhelmed by garbage. Commenting and being active in communities takes a lot of time, and as such, is more available to those with plenty of free time, so you’re going to get more privileged people - and especially, privileged teenagers - in comment sections. It’s a losing battle to try and take it from them. We have to build our own online communities where PoC, LGBT folks, and other oppressed groups feel comfortable and where their speech can’t be drowned out by bigots. That, I believe, is one of the mission statements of this place where we’re writing.
Another thing, specifically about YouTube. It’s impossible, at this point, to ignore how much the current landscape of YouTube has been made worse by the way progressives have chosen to interact with it. YouTube encourages, through its algorithms, content based on drama and personal conflict. My video titled “OWNING THE SKEPTIC CRACKER”, full of mockery and some perfunctory critique of Mr. Cracker’s ideas, is much more likely to get attention than my video titled “Why Skeptics Are Wrong About X”. The result is that a lot of progressive YouTube work targets particular right-wingers.
However, far from dampening their influence, this actually creates a dynamic that increases the pull of both progressive and reactionary channels - and the more that terms are equalized, the more privileged people maintain their advantage. Worse yet, it means that progressive YouTubers often find themselves more dependent on reactionary vloggers than on developing their own politics, which leads to the unfortunate phenomenon of leftish YouTubers starting to become friends with all manner of bigots.
The solution would be to resist the algorithms and to stop giving the reactionaries attention. Sadly, with most of progressive YouTube, this is very unlikely to actually happen.