I wish there was a way of making misinformation a punishable offense. (cue people moaning about misuse, who decides what is misinformation etc which is why I said wish). At the moment people can publicly and on-the-record spout the most outrageous bullshit and even when they get proven wrong there is no repercussion. none.
On a personal level, just cut those people out of your life. Refusing to interact with people who knowingly lie and knowingly spread misinformation is the only rational choice. Time is our most valuable resource, spend your time on projects and people who will carry us forward rather than wasting time on people who are just worthless timesinks.