Except that bluntness is not useful truth in opposition to pleasant lie.
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".
Even if bluntness only equals useful truth for a minority of times, it is still worth it.
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, 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.
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".