Below is one of the best explanations I've seen, and a great argument to NOT identify with any political party. I don't talk politics with my friends. I read a wide variety of news media, and then I vote in private. With my friends, I like to have conversations about art, travel, and business.
MIT Technology Review: How social media took us from Tahrir Square to Donald Trump, 2018-Aug-14 by Zeynep Tufekci
While algorithms will often feed people some of what they already want to hear, research shows that we probably encounter a wider variety of opinions online than we do offline, or than we did before the advent of digital tools.
Rather, the problem is that when we encounter opposing views in the age and context of social media, it’s not like reading them in a newspaper while sitting alone. It’s like hearing them from the opposing team while sitting with our fellow fans in a football stadium. Online, we’re connected with our communities, and we seek approval from our like-minded peers. We bond with our team by yelling at the fans of the other one. In sociology terms, we strengthen our feeling of “in-group” belonging by increasing our distance from and tension with the “out-group”—us versus them. Our cognitive universe isn’t an echo chamber, but our social one is. This is why the various projects for fact-checking claims in the news, while valuable, don’t convince people. Belonging is stronger than facts.