The other weekend, the neighbors behind-ish (staggered) us were having one of their loud parties because they want to infect all their friends I guess. I looked, there's almost no noise ordinances so I just have to live with their mayhem.
Wife told me to go outside. They are passing around to the drunken folks an airgun, shooting at a target taped to a tree in their furthest back yard. Yes, between us. I and another neighbor are downrange of a terrible backstop.
They saw me on the deck, waved, I said "NO. No. " and I forget what exactly but none of that. You are shooting at us and it's not allowed in the city anyway.
So, I generally grumble, gripe online, and glare, but do not talk to people if I can avoid it. But I guess that answers: at least for safety issues involving me, I will apparently speak up to people I don't really know.
ETA: Bullets are supersonic. If someone wants to play with a knife or axe or chainsaw out of range of me or my family, drive on. Who cares. But as a few have pointed out, even unsafe behavior pointed elsewhere can be unsafe behavior pointing at me without notice. Bullets even go /through/ things, so a neighbor unsafe in his yard is probably unsafe in his house, etc. A reminder was needed.
It's too bad everyone interprets the big-boy-rules and personal-responsibility as "I can do whatever I want, you can't tell me otherwise."