I'm facebook friends with several of these people, mostly from from high school. The **** they post is unreal! I also have friends and family with polar opposite political viewpoints and belief systems. Between those, I do my best to stay out of the fray.
It does become annoying some of the things you see, but I find it important not to block or un-follow these people.
One of the bigger problems we have as a society is confirmation bias and living in silos. Whether intentionally cutting out opposing viewpoints and ideas from your social media feeds, or having it subconsciously happen via Yahoo or Google's algorithm's, large portions of this country are living in echo chambers. Any opposing viewpoint is an attack.
It's good to remind yourself that these other ideas/people exist, even as crazy as they seem to me (or others), to keep the right perspective on things.
Extreme (but related) example, just think if everyone blocked the 'weirdo', or 'nutjob', or 'creepy guy' from high school, that always seemed a bit off... it's possible that nobody would see any of the warnings signs for the next mass murderer.