I have to disagree. He didn't have to bow at all to send that message. There is respect and even a hint of reverence in Doom's posture and words, and more is shown in the Genghis's response at Doom's graciousness and lack of duplicity. These are men who know what to look for in even the slightest of gestures.
"respect for certain protocols... if not for the men who require them."
This could be interpreted either way, and I have to assume that Doom is referring to other world leaders "as fools beneath him", but Doom is granting the humblest of tributes to one who knows Doom's nature very well.
There is no malevolence or haughtiness in Doom's face in the following panel... more importantly, his eyes. None of the other mages get such respect from Doom, only the Genghis.
"Your summons intrigued me."
Doom is not demanding to know why he was called, he is expressing polite formality as old students do of their former teachers, when called upon. Not so much for the Genghis himself but because of the Power backing the Genghis.