We also do it to ourselves. Everyone has someone in their life they’d rather mute. But they’re forced to coexist with them. Online is so appealing because you can find communities of like minded individuals. Then forget all about those other opinions you don’t like.
You grow in this bubble as they grow in theirs. By the next time you’re forced to interact, you feel so alien and unpleasant to one another it’s confusing and frightening. Corporations are right there to sell you on a story about how the other side are demons destroying the world. We gobble it up.
It’s still ideas the group agrees with. The idea is: that we all disagree with this idea. It’s subtle, until you look at the same story on CNN vs Fox. Two bubbles discussing the same issue with two VERY different emotional valences.
To put it another way: the discussion of these ideas that are oppositional to the community, is not with the intention of seriously considering them. It’s with the intention of dismissing them in a group act of catharsis. It maintains the bubble and safely dispatches an idea that threatened to burst it.