Bluntness may not be likeable, but you can often learn something useful from it, even if it feels offensive.
Majority of times it is euphemism for "insulting by making untrue statements, literally lying to get back at someone, exaggerate to vent own negative emotions".
Truth is a rare and important commodity, much like gold is. You would not throw away a mineral that has "only" a few per cent gold as useless, only because non-gold forms the bulk of it.
My point is, being jerk should not be equated with truth and people who are not jerks pretty often don't lie.
My point is, the most valuable insights regarding myself and my behavior came from people who were willing to be blunt with me. I would be a worse person today if I never heard some of the observations that made me swallow hard and even get angry.
Rather, give a person a mask and they'll tell you whatever will most further their own goals, be it truth or falsehood. If only the complete absence of accountability were sufficient to ensure truth.