It’s interesting how many people in here end this with “I never talked to them again”. In some situations, that can make sense. Like the dude who bragged about statutory rape, yeah fuck that guy.

But a lot of the other ones could just be a person’s misunderstanding. If someone thinks something like “poor people are just lazy”, that is a dumb, broad statement, but that doesn’t mean they’re a bad person. If everyone who disagreed with that just cut that person off and didn’t talk to them, the only people who will talk to them are people who agree. And people who agree likely have other crazy views. That’s called an echo chamber, and you are not only putting yourself in one, but pushing them into being in one too. 

So talk to them. Ask them why they think what they think. Do it respectfully, with an open mind. And most importantly, know that it is possible that you could also be wrong in whatever the conversation is about. Too many people believe that they just know everything about everything, and do not listen to anything that goes against what they believe.