that arguing or confronting some people is a total waste of my time and sanity. I will discuss politics any day with someone who can have an open discussion free of hatred and anger.....but that is getting harder and harder to do. I know the people who I can talk to and those who I will not bother with. My only purpose in discussion is to enlighten to facts or change a mind. When those things will never be accomplished, I just ignore those people. The only exception to that rule is if there are several people around who may be influenced by the discussion/argument.....you know, like they will see the wingnut as extreme and full of hate and my position as reasonable.
It sounds like your family situation is such that there is no reason to open that can or worms. Hide those people on FB if you don't want the controversy of defriending them. Or defriend them as your only statement on the issue. I have several people on FB who are extremist right wingers, and I usually ignore those posts they make. Occasionally I throw my two cents in just to get them to show how ignorant they are---and they never disappoint me. I figure there are many other people who are reading the exchanges. But you can't do that because of your job, so you have to ignore them, hide them, or defriend.
BTW, my sisters are the only family I have left, and they are wingnuts. There have been horrid fights in the past, and I have always regretted going there with them. We no longer discuss anything close to politics. Just for you to think about.