Proverbs 27:6
Solomon describes wounds from a friend are faithful - but how can someone who cares for you, harm you? Perhaps, that is the true measure of friendship - someone who is willing to tell you what you don't want to hear! Many will simply agree with us verbally but will withhold there true opinion, simply not to hurt our feelings. However, a friend will "call a spade a spade", even if it is not what we want to hear.
One additional factor in a friendship is the delivery of such bad news - it is not with contempt or humiliation. But rather with love. And if that love is based in Christ, it is a healing love, regardless of the severity of the topic.