It's a false dichotomoy.
In my experience I've dealt with a lot of very sh*tty police officers. The job attracts a lot of ego-driven, power hungry, validation seeking people by it's very nature. The job of a police department is important in a society like ours, of course.
But because I might need them to show up in an emergency, does that mean I cannot be critical of them? That I cannot dislike them in general for their behaviors during their other duties? Or in this case, off-duty?