To be clear, I do not think ( nor thought I said ) the Consult are the "good guys". Good points on the depravity, that appears unconjunctive ( but maybe not - I couldn't follow the Mangaecca logic of distributing "lunatic misery" on innocents to prove they feel nothing from it after viewing the Inverse Fire - guess was validation for them the "truth" of the Inverse Fire - regardless, still seems unnecessary for the shutting the world application ... just spitballing here, maybe demonstrating extreme depravity illustrates their invisibility to the gods, otherwise they would do something about it ). My point wasn't about what the books were stating damnation really is in the story either - agreed, we still don't know for sure. BUT - it is being touted among the characters that it is eternal torment, the Consult seem to believe so saying they see themselves suffering horribly in hell, which denotes "conscious" of that suffering. The Consult believes they're screwed - eternally. While shutting the world shut is unarguably evil, if they can't find another way to avoid it, then mass murder in the millions is not out of bounds as a legitimate avenue ( if it would even work, but they mention breaking the soul chain - still not sure what they're getting at there, which supports your possibility of the soul returning to a new body/reincarnation - which would mean they don't have the shut the world after all ).
I agree, still unknowns abound - just speculation on IF eternal damnation is eternal suffering consciously experienced, then they are panicking and not necessarily evil to pursue any avenue with promise.