Ethical dilemmas don't have to involve killing: firefighters are also trained to make rational (rather than emotive) life and death decisions: it may be better to leave resuscitating the baby who is seriously injured and concentrate instead on rescuing 2 adults still caught in the wreckage. Here training has an impact on the nature of the decision making process. Indeed, I recently heard the wife of a firefighter say that she had noticed his rational mode of decision making spill over into his personal life as his training became ingrained in his psyche.
Botogol, I enjoyed the piece immensely and found that it made me reconsider my own instinctive "of course you would push the fat man" response, having done the maths. If I truly, actually, honestly imagine myself in the exact situation, with a particular fat man in front of me (not a general fat man), then I am NOT so sure I could do it, bearing in mind, as you pointed out, that, like you, I wouldn't even have the moral courage to be rude to somebody in the ordinary course of events, even when it might serve a logical purpose. It's partly the jump from the generic to the specific but perhaps that is the same as the jump from Far to Near.
BTW, MatthewB, I think the point is that the man is fat because it takes someone OTHER than yourself to stop the train - self sacrifice is ruled out as an option so the soldier has to also decide between the fat man and the 5 railworkers.