I watched "High Noon" (
synopsis)with my Hungarian classmate/roommate. It turned out to be an educational experience. She didn't like it much, because she felt it expressed morally repugnant American attitudes toward interventionism.
The way she first phrased her objection was that she thought Will Kane was being portrayed as a hero even though he did something morally impermissible. After all, he could have fled the town hours before the train arrived and thus avoided bloodshed. And if one can avoid killing someone, then one must do so.
This lead me to think of the following scenario: suppose a space capsule is off-course and has a 75% chance of landing near enough to the location of your houseboat so as to kill you if you remain there (while leaving the sole astronaut inside unscathed). But the capsule is three hours away, so you have time to move to a location where the probability drops to 1% - that's the farthest away you can get. Your houseboat is armed with surface-to-air missiles. So if you're ever in imminent danger of being killed by the capsule, you can destroy the space capsule with your missiles.
My roommate's position was that you must move as far away from the capsule's path as possible, but once you did so, it would be permissible to shoot down the capsule to save yourself if it ended up heading your way, presumably because you've done all you can to get away from the threat.
I thought this might be inconsistent with her living in Los Angeles. After all, the chance of being put in a situation where killing would be morally permissible is much higher in L.A. (let's say, 0.01%) than it is in, say, Vancouver (0.0005%). So if you could make it 20 times less likely that you would be in a position to kill somebody, it seems you must do so.
This is obviously a ridiculous conclusion, but it's not clear what, if anything (since disanalogies abound) is wrong with my roommate's reasoning. She suggests that there is some threshold beyond which one need not reduce the risk, and that seems sensible but ad hoc. What I find more plausible is the suggestion that in none of these cases do we have a duty to remove ourselves from harm's way, but that it would beneficent of us to do so. But that's just the beginnings of an answer.