We have to remember that we're all brothers of iron. Non-positive/unproductive comments go deep, like a deep muscle burn you get on your 5th set of a reverse pyramid workout where you have to do 20 reps...except instead of making our muscle grow and get huge...they make our egos shrink and get smaller, which in turn could affect our workouts, which in turn could effect future epic gains of mass and vascularity.
So when a negative comment is made, it not only hurts someone's feelings...it also hurts their bicep peaks.