I am a progressive, so liberal I verge on socialist, and I think one of the "Left's" great flaws in the US is its inability to walk away, to just ignore. Engaging vociferously is seen almost as a moral imperative; "we must fight evil wherever we find it" sort of thing. But all that does is bring attention and a form of validation to the more lunatic attempts to enrage them. They aren't accomplishing a single thing by getting so righteously angry over statements the speakers probably aren't even making in good faith.
You can even see in the memes. It's the right that loves "trolling libs," and the left that's taking the bait. I think it's telling that the stereotype hardly ever seems to go the other way; you almost never see people talk about liberals "trolling reps."
You really don't need to engage with everything in order to be a good activist. In fact, I believe taking time and emotional energy to do so is actually being a bad activist. You're just wasting effort, nothing you say or do will change anyone's minds because mostly, the whole reason they're saying whatever it is is specifically to make you upset. To trap you into unwinnable arguments just to laugh at how heated you get.
Really we all need to be better at just walking away from crazy, whatever side of whatever spectrum we find it. By regularly surrounding yourself with such conflicts and by regularly basting yourself in such a soup of intense negativity, you are quite literally doing nothing more than causing physical harm to your body and mind via the morass of cortisol, etc. you are unleashing. You are accomplishing nothing.
I agree that Facebook makes this painfully easy, although Twitter and Reddit are right there as well.