The legal/judicial system in many countries is questionable and there's many faults, there is no doubt of that. It it acceptable to do the best they can with it? I mean the government administrators...I don't know. Maybe society deserves more...but nothing is ever perfect right?
As someone else commented, society seems to see a police badge and forget that that person is a human, has a family and friends and does a very tough job. Sure, they know the risks going in, and yes, there are some very corrupt individuals (and departments) however in the main they do a job that many cannot or would not, the same as military people.
I guess it comes down to each and every one of us...human beings. if we all did the right thing, to the best of our ability, the need for law enforcement would diminish, not go completely, just lessen. But, that's not going to happen because it's in humankind's nature to be selfish, egotistical, greedy and hubristic.