He pistol was used in self-defense to stop the ongoing assault by the man who was offended by the bumper sticker. The pistol appears to have been effective in bringing the unprovoked assault to a sudden end.
Pistols tend to do that, don’t they??
When the initial aggressor said to the other that “people like you should be shot..” he was making a threat.
I would acquit the bumper sticker owner .