A pastor friend of mine asked this question on Facebook:
I can't say I have blocked anyone for that reason yet, but there have been times I thought I would have to do so. But it's not just a FB phenomenon.
And it's one of the hardest things I have to witness. So many think that whatever makes them "happy" must be the right thing to do, even if they know it's wrong. You know, the logic of the old song that said, "If loving you is wrong I don't want to be right".
And because they won't listen, even though you try, they continue on their self-destructive path. You know where they're headed, but because they feel good at the moment there's no desire to turn around.
All you can do is shake your head and move on, I guess. Hopefully one day they'll get it.