>1. Whose role is it to make judgements about whether people should be able to find certain kinds of content?
Well for starters, there's the user. Once youtube decides you like a certain type of content that it wants to amplify, there is no "ok enough of this" button. You can't dismiss the categories it makes up for you.
And for enders, well your real question comes down to the question of if sufficiently effective psychological engineering contradicts, at least for some large fraction of people, personal agency. Suppose there was an adversarial patch we discovered that you could hide in a banner ad to make 15% of people read a completely different article than the one that is actually in front of them. That's may not be a highly efficient hack, but its more than the margins on nearly any election. How do we police these newly discovered neural-network hacks?
There's no question in my hypothetical on the matter of the victims personal agency in forming opinions and seeking information. I took care of that in the premise. They have no control, its a design flaw in the brain that is being exploited. But, where along the continuum of plausible technology does one draw the line between brains being hacked and people having agency in what they choose to see and believe?
I don't know either.