Not just intellectually but also politically (which I dont find to be particularly intellectual). By being surrounded by "your own" you live in a filter bubble that can only make you more extreme / radical. Basically all your friends vote the same as you but some do it more loudly and obnoxiously.

You miss the fact that regular people on the other side are just normal people with slightly different policy preferences. ie - they might agree climate change is real, but aren't rich enough to profess it as their #1 policy concern.