It's just as imperative to make sure space aliens weren't involved, except space aliens aren't part of the leftist agenda.
We're talking about a group including the avowed mastermind of the 9-11 attacks. I'm supposed to get all worried about the death penalty in this case?
Unfortunately, there are two types of torture. If they torture a terrorist, and he reveals a terror plot and lives are saved, that is, I suppose, "good" torture.
Then there is the type as practiced by the Soviets under Stalin in which they tortured a person who would confess to anything to put an end to the torture. No information is discovered in such torture, and the victim reads a list of his offences during a show trial and is taken out and shot . You basically inflict enough pain that the torturee begs for death. This is "bad" torture.
And innocent men captured by warlords and turned over to Americans for bounty, later released after years at Guantanamo.