It's a very common French saying that
"il n'y a que la vérité qui blesse."i.e. only truth hurts or, better, nothing hurts like truth.
This is especially true of psychological truth when someone challenges an element of your character or personality and you are hurt by what they have said. Chances are what they are saying has truth in it - would you be upset if a comment on your person was obviously false and therefore unthreatening to your self-image? - and you have yet-to-resolve issues/demons to address including that of pride (which, as I have said many times before, is the opposite of self-esteem).
Anyway the insight that nothing hurts like truth would give weight and reason to Plato's observation that no one is more hated than he (or she) who speaks the truth, be it political, psychological or philosophical. For people react violently to what hurts them.