>Except it's not up to you to decide which of these two will die

I'm standing next to the track switcher, so I'd argue that it is.

Heck yeah it's my decision! I don't want to live in a world where decisions are made like this, but in this case we must accept our role as the lever puller. Or walk away I guess, but that's no different from actively condemning the litterless person.

What if the problem is rephrased and inaction would mean death for both?

if inaction has same result as action then it's better to stay away from any responsibility caused by action