The Wapo article in question

Idk which moral system you operate under, but I’m concerned with minimising human suffering. That implies hitting kill because chances of a mass murderer are too high not to. You also don’t follow traffic laws to a t, but exercise caution because you don’t really care whose fault it ends up being, you want to avoid bad outcomes (in this case the extinction of humankind).

Why do you care whose fault it is? You’d want to minimise human deaths, not win a blame game.

It does create the funny paradox where, up to a certain point, a rational utilitarian would choose to kill and a rational mass murderer trying to maximise deaths would choose to double it.

You would need a crazy low probability of a lunatic or a mass murderer being down the line to justify not to kill one person

Edit: Sum(2^n (1-p)^(n-1) p) ~ Sum(2^n p) for p small. So you’d need a p= (2×2^32 -2) ~ 1/(8 billion) chance of catching a psycho for expected values to be equal. I.e. there is only a single person tops who would decide to kill all on earth.