This reply is to clarify what you posted. First of all I think you are saying that it is unwise to brandish a firearm to scare someone. I totally agree with you on that point. However, I disagree with your statement and the idea "if you are going to draw it use it." I think a better way to look at it is... If you are going to draw it, be prepared and intend to use it if you need to."

Most lethal threat encounters are quick and violent, but there is always the moment between clearing the holster, putting the sights on target (if you are trained to do so, hopefully you are) and pressing the trigger. So a person can conceivably draw a weapon, and the situation change. Such as the person turns and runs, or the "gun" he was pointing at you is really a cell phone. All this is predicated on the context of the situation and events leading up to the decision to unholster.

So, no, I don't think there is a mandate to use the weapon if it is drawn. There is danger in this thinking. It is not the case that "If the blade is drawn it must taste blood."

This is not to advocate brandishing a firearm. That would be tactically unsound practice and demonstrate poor judgement, however, I don't think that it is wise to make an ultimatum that "if you are going to draw it use it." To reduce this to the absurd, every time I unholster my pistol I have to crank off a round before I re-holster? I am guessing this is not what you intend to say.

There are many accounts of the decision being made to shoot and as the slack on the trigger is being taken up the situation changes and the trigger stroke is not completed.