No one expects perfection. Obviously. No one said anything about no mistakes. You pulled that out of nowhere. The issue is accountability for those mistakes. Of which there is not enough. Hence the current protests. What incentive do police have when they investigate themselves and there are no consequences, or slaps on the wrists, transfers to other departments, etc? You would at least get fired for repeatedly shipping buggy code and showing no desire to change it. Except in the case of the police, it would be like your boss investigating the bugs, agreeing with you that they are not in fact bugs, and saying good job, you did what you were supposed to.
No other job functions this way. Why do we let the profession with the power to use deadly force function this way?