Classic mis-use of double effect. @Rau essentially makes the same argument, but without explicitly quoting double effect. You could just as easily claim that “performing surgery is a morally neutral action” or “using a scalpel is a morally neutral action”. The trick (in making this type of claim) is to focus in, so narrowly, on the act, so as to divorce it from its context. “Throwing switch” sounds a lot nicer than “directing train onto track with man tied on rails”.
OK, fine: the ‘good effect’ is “train doesn’t kill people on track A”; the ‘bad effect’ is “train kills a person on track B”. The bad effect is the means by which one achieves the good effect.
So… by rerouting the train onto track B, you do not intend to doom the person tied to track B?
Here’s where your argument really goes off the rails, so to speak. DIsproportionality is not merely “body count”. Your analysis, which really boils down to “one instead of five,” is utilitarian/consequentialist at its heart. As such, it does not work in the context of Catholic moral theology.
The second one is the difference between the two scenarios. In the surgery, the other patients are actually saved by the harvested organs. In the trolley situation the four on the track are not saved by the fact there is another person on the other track. They would still be safe if no one is on the other track.