Many times, most times, when a thug threatens you (by words or posture) with imminent bodily harm, he has already formed his intent to hurt you. He is not open to hear your logical or emotional appeal of why it's a bad idea, or civilly discuss with you the pros and cons of beating your a**. One's attempts to do this will only serve as a source of entertainment to him and build his confidence. The case where this may be helpful is when a trained fighter is trying to lull the attacker to lower his guard, thinking he has easy prey, their favorite kind.
"If you seek peace, prepare for war." More often than not, displaying strength, and the will to use it, will prevent aggression. Something many of our leaders seem to forget throughout history.