Right, but everyone thinks of themselves as good people. The chiefs who resigned for being overtly racist would have lumped themselves in with the good cops the day prior. And very few people will label others as "definitely bad people." It's easier to stay on the line and be half-friends with everyone.
Asking people "Who's good?" won't reveal much. Asking "Who's racist?" or "Who's had the most accidents?" or "Who wouldn't you want with you when you're pulling up on someone?" are much more telling. Not just for police- for any group of people.