"Online you are constantly confronted with opinions and world views that are not your own. It turns out the place where you are the most ideologically isolated is your real life... your filter bubble exists in your real life, not online."

...

"Whether you want it to or not, your brain sorts people by world views and opinions, into teams... called social sorting. Because we're missing the social glue the disagreement becomes a central part of their identity and this will make it less likely that you will seriously consider their position or opinion in the future.

If you hear bad things about them, your brain is much more likely to believe it uncritically. On the flipside, there are people [online] who share your worldview which makes your brain like them a lot and hyper allign with them.

Social media optimizes the worst disagreement possible... and assigns it everybody on the other team."