Social pressure alone, however, might be enough to spur Google to either modify its targeting, or to make an easy and obvious way to turn off targeting.
The bolded strikes me as insufficient.
Arguably we don't get the societal benefits of removing targeted search results if it's an opt-out system unless you can "opt out" on a per-search basis. Something like Google having a button at the top of search pages, "Show untargeted results". People will play with it just to play with it, and that helps, a /little/ bit. Unfortunately, it still reinforces a sense of "Here's the real world, and here's the world THEY want you to see" -- with the two being swapped from their real order. After all, why would Google by default feed them biased information? Especially if it happens to perfectly fit their contrived worldview! Bias is something that happens to The Other Guy -- you might be aware of bias on your end but the average person convinces themselves that awareness of bias is enough to counteract it, according to my research and experience.
Another issue is: if it's opt-out, most people won't bother -- it's extra work, even if it's minimal extra work. Witness how few people (outside the scientific community, of course) will bother using something like libgen if they want an article that's paywall locked. Slight inconveniences are sufficient deterrents for the average individual, there's a lot of evidence of this.
(I think there's something to be said for the other side too, though -- people who are used to digging for information feel like information they get "easily" is somehow worth less. I know I've noticed this tendency in me, and I think it's something that could backfire in a world where this sort of thing manages to get pushed through.)
I've thought about this, and I think I'd prefer default untargeted search results with opt-in targeting on a per-search basis. That's the best of all possible worlds, I think -- it gives P3nt what he wants with a single extra click per search (reducing the work of hunting through untargeted results despite the minor increase of work to bring up targeted results), forces no extra education, and says "This is the real world. Here is the fantasy world we have prepared specifically for you" -- which raises awareness of how prevalent the echo chambers we live in really are.