Eliphas Levi is wrong then. That premise is far too thin to stand, it drops scope. Stalin [insert very bad historical person here] could have certainly utilize

Eliphas Levi is wrong then. That premise is far too thin to stand, it drops scope. Stalin [insert very bad historical person here] could have certainly utilized reason in the course of pursuing evil actions for example. The scope there is narrowed down to specific actions. If you broaden back out, you can say that Stalin is acting irrational by committing heinous acts in the first place, but that's only the case if you're defining the standard of what is good on his behalf (as opposed to what he may consider good to be). You'd be imposing your standard, the foundation of your morality, on him. Morality depends on first defining the standard of what the good is. From there you can extrapolate the rest, you can construct a system forward. Stalin and I will disagree on the standard of what the good is, and as such we'll reach different conclusions on a lot of things. From his standard, he can take rational actions, make rational decisions that align with his aims - they're rational as it pertains to what he's pursuing, what his standard is. One can entirely disagree with the standards that someone else holds, of course. Their behavior may be evil by your standard for example, and vice versa. You could argue that there is one objective standard for The Good (thus everyone else not following that is immoral to the degree they diverge), however good luck convincing most people to go along with that (it'll never happen). Is putting these people in a gulag rational? Well that depends on what you're trying to accomplish.