The Absolute cult are a group of puppets that may also be a Mind Flayer sleeper cell where at the time and place of their choosing they'll hit a button and turn them all into Mind Flayers, as seen with the button on the ship. Nothing about that is a positive, our knowing simply gives us a chance to escape it. Again this is the core issue with working with the cult, they're deluded puppets with nothing of value to offer other than their deaths. Wiping them out isn't even good it's just the rational choice, they're screwed so you might as well put them down and prevent future issues.