Ads don't do that. Maybe you're thinking of organic posts, which are not ads? Or do you have examples of "extremist" ads?
Having worked on this stuff, I can tell you that the data relevant to extremist rabbit holes is not what the FTC is talking about. Facebook learns enough from which posts you click on to know which extremist content to suggest (and then they intentionally do not suggest it)
The necessity to engage people for the advertising business model to work does do this. People are naturally engaged by outraged, the algorithms “figure this out,” and systematically produce outrage. No ads, no existential need to arbitrarily increase engagement.
Having worked on this stuff, I can tell you that the data relevant to extremist rabbit holes is not what the FTC is talking about. Facebook learns enough from which posts you click on to know which extremist content to suggest (and then they intentionally do not suggest it)