ITC, you beat me to it. Folks going to Mexico used to ask me what they should carry for defense - I told them a fire extinguesher. If anybody asked why they had one in their tent (or motel room), just tell them you were burned as a child. At a car accident or "disabled" car, take it with you "in case there is a fire".
Whenever someone mentions knives, I ask if getting covered with the blood of a hype with HIV is part of their long term survival plan.
And if I got into an argument that heated that someone wanted to hit me, "Nike time!" It's just not that important, and besides, if you strike back, it can be considered 'mutual combat', and you become an agressor as well, liable for the injuries ultimatly suffered by the other combatant.
It's may not be considered defense of your life, if you stuck around to 'duke it out'.