The lightning example isn't really analogous. Sure, one or two people might get struck by lightning, but they're not then going to continue spreading lightning

The lightning example isn't really analogous. Sure, one or two people might get struck by lightning, but they're not then going to continue spreading lightning strikes once they leave my house. Moreso, those (non-existent) spreadable lightning strikes aren't going to mutate to get worse as they propagate. There isn't an easy or obvious answer to where it stops and how to determine that, but that goes both ways. We can't just have zero laws for fear that the laws might overextend themselves. Unfortunately, we have to deal with nuance either way.