I have been following along with some confusion. The way everyone is posting sounds as if the pre-emptive strike was a crippling or deadly strike. It doesn't have to be. You could send a front kick to the mid section, send a groin kick, a palm strike, etc., etc. If you have tried avoidance, verbal communication, and other tactics with no success, and you are backed into a corner with no where to go, you need to get out of the situation. It doesn't mean punch them in the throat and stomp their head in while their on the ground. If your unsure of their intentions, send a non crippling strike to get space and get to safety. If you don't do major damage to the person, you won't ever see the inside of a court room.
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If your in a "Fair Fight", your tactics suck.