The Personal is Political--issues of religion and civil rights are issues we get passionate about. I blame no one for feeling strongly about their views, even if those views are different from my views, which I also feel strongly about.
I am astonished, however, at the condescension I see on some of my friends' social media posts, by their supposed friends. Sometimes I can't resist the siren call to wade into the discussion myself, to dispute a false statement, or to support my friend against a troll. Then I find myself arguing with strangers and that seems pretty pointless.
When I see that level of gloating, hostility, or condescension, I can understand the unfriending after all. It's not usually the difference of opinion that is the problem. It's the attitude toward the other person. If someone is that disrespectful, that unwilling to even try to see the other perspective, then yes, I can see ending a relationship over that. It might be that the relationship didn't have much else going for it in the first place. None of us should tolerate abuse or disrespect. Disagreement, yes. Discussion and attempts at persuasion? At the right time, right place, and within bounds, yes. But always civil, polite, and respectful. Otherwise it's just harassment or abuse. Any rational person will limit that in their lives.