> Should people be striving to remove friction in discourse in the first place? I mean, if something hurts to hear, surely that should sound the alarm that it's worth confronting, rather than running away from, right?

Not necessarily. I personally prefer Scott Alexander's criteria for commentary at SlateStarCodex (http://slatestarcodex.com/). A comment should be two of: True, kind, necessary.

Plenty of things cause near-visible sparks when you put them in discourse, and most of them are mean, pedantic, or just not true. You're interested in the set of comments which are true and necessary, this is a tiny subset of the comments which cause friction.