I think the main issue, is the public comments on the news.
A lot of news, while interesting and useful isn't very worthy of comments or reactions of people. However nearly anything that goes on there will be a number of people with a strong feelings towards it, but with the size of a population a small minority will make a lot of noise. So there is a lot of noise from these small groups making them seem like the larger community is more polarized then they really are. Then this unfortunately loops back on people instinct to belong to a group, so they will support the nut jobs that they will side with on that topic, and they will support your or my crazy ideas on the topics I feel strongly about. Then we isolate the other guys and push them away from supporting details on your side.
If you talk to a politically polarized person, about a problem that hasn't been politicized yet, they often would think of rather moderate solutions for an off the cuff problem. However once it has been politicized their stance will change to be inline with their team.
Why do you think we have Flat Earthers?
Evolution Deniers lead to Global Warming Deniers lead to Moon Landing Deniers to Flat Earthers. Because it became a competition on who is more Anti-Science enough to join the Anti-Science group.
There are many other types of group of people who seem to want to be the most of that group, despite going too far.