User blog comment:Thailog/Ep. 202 "Earthlings" discussion/@comment-128.54.156.144-20120506165637/@comment-1770843-20120506172434

They may have known but may have decided not to tell John Stewart due to the circumstances of bein in mind control, a bigger question would be how the flip the guardians didn't notice that two Green Lanterns (Hal Jordan and John Stewart were both under mind control around the same time.