He displays an irrational degree of revulsion at the idea of killing people. One gets the idea that he would let five die in the trolley problem.

I doubt it; he is a self-described consequentialist, and doesn't seem to be unaware of the math or unwilling to do it.

(By the way, it's completely appropriate to feel revulsion at the idea of killing the one person in the trolley problem... as long as you feel five times as much revulsion at the idea of letting the five in the trolley die.)

Edit: The bigger problem with your scenario is that, if I remember correctly, creating a Horcrux requires genuine hatred and malevolence, not just any death.

Edit 2: According to the Harry Potter Wiki, it also requires some other unspecified "horrific act".

Edit 3: I wonder whom Voldemort killed in order to Horcrux the Pioneer plaque.