Marines escorting slave ships is so, so, so bad. Where is the moral greyness of the marines Oda? Even grunts have no excuse.
Akainu's reaction to Vegafraud's speech didn't help either:
But this can still go more than 1 way depending, as in Akainu with all his relentless dogma and thus obvious brainwashing, like a "good dog" is oblivious to who really rules the world, true history etc but he heard Vegapunk's speech too and I do feel he knows more than he lets on especially since he's Fleet Admiral now, has spoken to the Gorosei face to face and shit talked them too and so on. Oda won't give us anything on Akainu vs Kuzan, some people think Oda showed Imu in Kuzan's sunglasses at Punk Hazard which I seriously doubt is actually true/deliberate on Oda's part too.
There was corruption shown in the Marines from Morgan in the beginning to Nezumi but also them willing to partake in Buster Calls and do anything Celestial Dragons demand them to do. The moral greyness feels more like an small exception rather than a more widespread standard in the Marines sadly.
Them also hunting down and killing countless infants and pregnant mothers says it all too. Very 10th Plague in Egypt too. Genocide of the first borns by "God".