The trick is to have no more than 10-12 Facebook "friends."
In my case, that's my immediate family and three or four boyhood buddies.
I sympathize with the OPs sentiments, though I would describe my experience differently. There are one or two hardcore, virulent, vocal leftists in my family, who constantly post trivial (i.e., insubstantial) anti-Trump memes. When I attempt to engage them in polite discourse, pointing out that the memes (**best Perry Mason voice**) make claims based on facts not in evidence; are irrelevant, incompetent, and immaterial; are riddled with fallacies; etc., they reply with ad hominem attacks and threats (equivalent to the argumentum ad baculum) of the withdrawal of affection ("How could you defend such a man?!" "I expected more of my brother!", etc.).
Then, the rest "pile on."
Given the choice, most people will choose the "path of least resistance," which means agreeing with the majority - also because it "feels good" to be so righteous and generous (with other people's money).
Regards,