He specifically also thinks that the internet is dangerous because it permits only SIMILAR people to exchange w/one another, ergo democracy is ILL SERVED.
He introduces in one of his books the idea of “Cascading threshold” —that’s where people (by hanging out with similar people) see some unsupported (or even ridiculous) idea (like low taxes encourages prosperity) sooo often that they simply reflexively believe it.
He also once called himself something like, a “choice facilitator” —kinda like when your mother told you you’d eat broccoli....or BROCCOLI.
See? Your meal choices were transformed from confusing (ice cream, PB&J) to crystal clear.
Here is a link to the abstract of the academic paper Sunstein wrote called “The Law of Group Polarization” concernng this phenomenon. He uses trigger words like “polarization” and “cascading threshold”.