If you've ever had a boss say something mean to you, it's likely that you still remember it vividly. You probably won't ever forget it.
Leaders do need to provide feedback and much of that feedback may be constructive -- coaching involves helping others improve their skills in order to achieve their goals -- but that constructive feedback can, and should, be delivered in a positive, dignified way. Not mean. Not nasty. Not insulting.
Words meant to hurt are better left unsaid.
-- doug smith