I didn't realize the Deo'lei were such a large organization ._.

Regardless, Shien hit the nail on the head, at least in Morgan's case: being "the bloodhound," Morgan was more of a tool vs. an actual thinking member of his squad. Even if other sniffers are usually treated better, Morgan was not. Also, when making Morgan's CS initially, I chose to place him in Seclyr because of their hate for magic (and anything associated with it), so that he would be sheltered from certain experiences, at least in his earlier years/time with the Seclyrian army. While he probably would have heard the deo'lei, it's safe to say he believed them more of a legend/hyped up order than anything else.

That being said, Morgan's only encounter with the deo'lei was with a demonspawn was after his time in the Seclyrian army as a sniffer.  I haven't fully plotted out the exact happenings of the encounter, but I'm going to assume that the brush with said demonspawn was impactful enough that 1) he assumes that the deo'lei are all demonspawn 2) they all wear the badge mentioned in the IC post. He just placed two and two together from past experiences and believes his information to be fact.