It's just an extension of high school. The extroverted leader of the popular kids spreads falsehoods about everyone not in their group relying on followers not to question them. For the most part, the lies are embraced. The only solution is for people to think independently and question authority. That's hard work that requires skills many people don't learn in school. That's why there are people, currently benefitting from Social Security and other social programs, who believe the fearmongering of leaders who say America might become a communist or socialist nation. The long-term solution is education, not just facts or even concepts, but also attitudes about learning. That change is generational.
Is there a short-term solution? There's no ultimate authority who can step in and correct bad behavior (where is Gort when you need him?). Joe Biden seems to think that bipartisanship is the key. Maybe if we had more "have you no shame" moments, perhaps from rational Republicans like Romney or Murkowski, people might reconsider their beliefs. There are just an awful lot of Joe McCarthys that need to be confronted.