That's because saladin still views light & dark as good vs evil instead of what they really are. Grey. Neutral. Ton of lore where lightbearers were awful people. Everyone knows about rezyl azzir (dredgen yor). The powers of darkness & hive magics were thought to be too dangerous & anyone who wields these powers will be corrupted. Which is true. But the guardian, Eris morn, Elsie bray, & drifter show that it is possible to not succumb to that temptation. TL;DR I highly doubt caitil is planning to turn on us & this is just Saladin trying to tell shaxx without telling shaxx check your girl caitil lol