I have to disagree with you a bit on that. Most self defense/lethal force laws are conditional with words to the effect of, "the person had reason to believe that their life or the life of another person was in danger." You may be justified in shooting an intruder in your home walking toward you with a screwdriver in his hand, even if his intent was to steal the screw driver, and not confront or harm anybody. A number of people have been exonerated in self defense shootings after it was demonstrated the assailant had a toy gun, cell phone or other "non-weapon" merely because the person exercising their right to self-defense "believed" or "perceived" they were in far more danger than they actually were. The problem is how much common sense is exercised in enforcing and prosecuting conditional laws, as is the case here. The police should have explained to the complainant that the man was exercising a constitutional right, and as long as he wasn't brandishing the weapon or making overt threatening gestures, he was no more dangerous than any other person in the supermarket with a set of car keys.
Your point is well taken. Nonetheless, a law, or the interpretation of a law by a policeman, that depends on the feelings or whims of another are generally letting individual rights be overturned by the masses. In your case, an individual right, the right to self defense, is upheld.