Jokes aside, why does it matter that Advertisers are not choosing certain 'unpalatable' bubbles to not be associated with those channels, that's perfectly fine.
You seem to be concerned about extremist videos making money, I don't care about that at all. I just want all videos to be available unless legal system demands its removal after due process. Present sanitized content by default, present all content if explicitly requested, where an action from user says they want to see offending content.
Advertisers should be allowed to chose the channels that they advertise on. Some may choose to advertise on default channel before the content is flagged. Let the buyer make the decision. Why is YouTube giving in to certain vocal Ad buyers to decide for entire Ad market?