There is a beauty about objective feedback. Sometimes it hurts, but it's objective, and it means something. If you can take negative feedback, even when you want to emotionally retaliate, it will do eons for what you can achieve.
According to recent studies, you shouldn't worry so much when it comes to pointing out mistakes to someone who is experienced. Negative feedback won't crush their confidence, but it just might give them the information they need to take their performance to the next level.
My passion and my career revolve around designing group situations which inspire people to create greatness with minimal stress. "American Idol," for better or worse, is role modeling exactly the opposite.