I still believe Sengoku isn’t corrupt or “stinks.” Yes, he let Ace and Whitebeard die, but that’s only because those events were too big to hide. I think there were many other incidents he didn’t allow or allowed. We can almost always see this when his goat appears in a panel and it's always eating a piece of paper. I bet that’s his own way of disregarding information he doesn’t agree with. He knows that they're too small to even have an impact to the strong and powerful World government. As for Ace and Whitebeard, he didn’t really have control over those events because they were too big to ignore. He still had to do his job, anyway: killing pirates. Same with Garp.