ClydeFrog,
If I find myself confronted by a couple panhandlers in a Wal-Mart parking lot, late at night, and notice a third moving out to my flank, and should they ignore my verbal requests (then commands) to cease... should it be a crime for me to show a weapon, in pursuit of encouraging all three to stop what they are doing?
Depending on the jurisdiction, if I can't show that they were a direct threat to life and limb, I could easily be charged with brandishing.
Now, you and I both know that maneuvers of that sort are typically the prelude to strong-arm or armed robbery; I for one can certainly state that in very precise terms, and I can point to formal training about such things to back me up. A lot of other folks could not so articulate a scenario, though their intuition would have correctly identified threat behavior - and such people are much more likely to be charged, not because they did anything wrong, but because they can't explain why what they did was justifiable.
You keep throwing around terms like vigilante, and wannabe. Please share your definitions of vigilante, and of wannabe, and let me know what either term has to do with showing of a weapon as an attempt to deter a building threat.
I do have to wonder about your motivations. Back when I was studying psychology, much was made of "projection," or the tendency to see others as likely to behave the way we think we would, if we could.
My counter-argument is that if the law clearly identified situations where showing a weapon would be justifiable, it would prevent people from being charged for having tried to head off a problem before they were actually forced to open fire.
With regard to warning shots, I don't generally agree with those. I can see some utility, in some scenarios, but those generally involve packs of aggressive canids, and a good backstop. For the most part, otherwise, I consider warning shots to be reckless (where is the bullet going?) and a waste of good self-defense ammo.
But I can see many scenarios where showing a weapon might very well stop a scenario from escalating to the actual need to use deadly force - with the caveat that the person showing the weapon had better be ready to use it if the show of force does not stop the escalation.