The problem is (at least in part) the two party system. It really helps fuel the us vs them mentality. It allows people to write off people's opinions with a broad stroke. For example, "Oh, that person is Republican. They must be racist and hate poor people," or "That person is a Democrat, they want everything handed to them and an authoritarian state." Both of these statements clearly do not represent the average person on either side.

Opinions are a spectrum, but we are constantly blasted with the extremist opinions on both sides. Social media has only amplified these issues. Extremists generate many responses from both sides and thus a lot of eyes end up on these opinions. Talk to your neighbor. Regardless of their political affiliation, they're probably a pretty decent human being (obviously there are outliers). Just try to remember the person you're talking to is a human being and their opinion is probably more nuanced than you give them credit for.