I post stuff to Facebook that could get inundated with hateful comments. I have a pretty good idea upfront which ones those are. I go ahead and post them. At the first sign of flameage I turn comments off, with a simple explanation. "I turned off comments here. I didn't want to have a discussion about this, it's just an observation." I think this is totally legit and more people should do it. Really frees you up to say what you see.