My god... he has to abide Saturn's orders the same as he has to abide Akainu's.
It doesn't matter who gave the order, Kizaru would be distressed about killing Vegapunk either way, because again... Vegapunk was his friend and Kizaru literally comments on panel in the manga he would rather not kill him.
Kizaru doesn't comment "Oh my god, Saturn gave me a order, I need to accomplish so I get a promotion"
But keep up with your non existent point.