You're right, Aramaki was simply concerned that the world would start to believe that the greatest military power of the Marines is not even capable of defeating the commanders of an Emperor, let alone an Emperor themselves. That's why he was shouting those words left and right, trying to inflate his own ego and deceive himself into thinking that what happened at the Reverie was just "luck." However, even though Yamato and the exhausted retainers managed to bring him down again, Momo, a Kaido wannabe with newly acquired powers, made Green Bull look even more pathetic than Morley. Now, Green Bull, in a turbulent state of confusion and emotions, simply threatens to destroy villages where innocent citizens live just to blackmail and capture a Shichibukai, even with numerous elite Marines supporting him.
The man is indeed the worst admiral in history. His Haki is terrible, and he doesn't even possess a black blade.
He is truly pathetic.