Certainly dept policies and enforcement of those policies will help change the culture of what's expected. But you have the remember the position description:
Your entire day is meeting people who are possibly engaged in criminal activity. You must be able to discern whether their activity is criminal; you must be prepared by verbal or physical means to halt criminal activity, even when the person is claiming innocence or threatening you. You may be called to a house for a domestic violence dispute, be allowed in, and see four people. You may not know who called, who is dangerous, but you must control the situation quickly.
People will, in general, not be nice to you. People will hate you. People will fear you. People will treat you like absolute garbage. Sometimes it will be their personality, sometimes it will be their culture, sometimes it will be because you have made a mistake. It is likely that every day of your job will be thankless and unreasonably taxing on your psyche.
The job is important. For every drug dealer you capture, there may be 10 less kids starting a life of dependency on a substance. Your very presence can stop a situation from becoming violent. The job is thankless because you deal with the perpetrators, not the victims. But you need to know that there are victims, otherwise who the hell would ever wear the badge?
It's a terrible but necessary job. And people are human. I am not forgiving them for committing their own crimes, but I get how it happens. It takes a very special person to do the job perfectly. Cases of significant abuse are *relatively* rare given the variety of duties police have. Prosecute the people who have failed, but be respective of the ones who have not.