[twoquestions]

Continuing from this, as they push content on you that you don't want to see, you become used to it. It's the same as getting used to a new musical genre; at first it all sounds like noise, but after the 50th or so hour you can hear the important parts clearly. Repetition legitimizes.

Harnessing that, they (Facebook, other advertisers) can push what ideas they want you to think into your mind, almost without your even noticing if you're not paying attention, and work to convince you you're the outlier even if you reject what they're saying.

You're correct, and the more I think on it the creepier it gets.