The issue with cameras for cops is trust. The majority of people do not trust the police to serve and protect. Police taken as a separate population commit a lot of crimes murder, sexual assault, theft, you name it. This is from a group of people who have a reputation for covering for each other and are knowledgeable in how to manipulate the law.
The true scope of criminal behavior by the police is difficult to gauge. Officer Friendly does not exist. The real perception is trigger-happy cops. If you have a domestic disturbance, you need to think twice before you call the police if you value the life of your loved one.
We need the police, but we need ask ourselves who becomes a cop and why. Many truly do serve and protect, but many are authoritarian bullies who became cops to ply their trade. Pay cops a fair wage, weed out the unfit, stop the culture of coverup. Stop acting as enforcers for business interests and the rich. Serve and protect everyone. If that cannot be accomplished, put cameras on them.