People really get confused over “nice” and “good.”
“Nice” is just social adeptness. A way to act around people so they don’t hate you automatically as you go about your daily routine. It includes politeness and generosity.
Most serial killers are probably very nice. It’s how they gain the trust of their intended victims; getting them to let their guard down. If they weren’t nice, they would find it hard to get close enough to kill their victims up close and personal.
This explains why, no matter how nice some of the cops you know may be, none of them are good. They are like the sociopathic serial killer– nice, with an agenda of violation.