It all really depends on how corrupt those cops are. Even in some developing countries where the majority of police would be fired by first world standards, they're still needed. And tbh the funny thing is this old saw is what I learned from RW when it comes to defending Muslims, but the main difference is cops are still a boon to the society where Muslims are a dime a dozen.
I'd prefer to leave the Muslims out of this, lest the topic get diluted further. It sounds like you're saying that some amount of corruption in the police is tolerable since society needs them. That is different than your prior argument that most cops are good and even awesome and shouldn't be judged by a few bad examples (or the ones who make the news.) And I don't' even want to ask how much corruption is tolerable before it gets too corrupt.
I'm remembering a post I made in Gaion's thread about serving in the military, where I discussed the Good Conduct Medal as not really reflecting 3 years of good conduct but only 3 years of undetected crime. I think this probably applies to police work, too.
In the case of cops, I am not really comfortable in a situation where I have to encounter a cop who is carrying a firearm and can probably get away with simply killing me, if he feels like it or is having a bad day or if the situation is not really as it appears. If society expects me to put my trust and faith in a cop, I want a cop who merits that trust and faith. For instance, if I just got mugged by "that guy over there" and he happens to be a CI of the cop who shows up, or if the cop happens to be involved in drug trafficking with "that guy" ... well, it's not gonna turn out well for me, and I'd have done better not to have called the cops at all.
It's possible that you could get awesome cops to do this dangerous and yucky work if you paid them a lot more than we want to pay, but maybe not even then. Bottom line is, communities tend to get the kind of policing they "want." Or at least the kind of policing the city fathers want. Usually, that means a lot of moral and ethical corners get cut. In the US for instance, municipalities are getting tired of million dollar wrongful death verdicts and they are now moving to a position of "municipal indemnity" where they say "we hired this maggot in good faith and he passed his training with high scores at the Academy, so our hands are clean." And they throw his ass under the bus and let your survivors sue HIM for his entire net worth of $78.16 and that's all you get. And usually he moves to another jurisdiction 25 miles away and THAT police force is happy to hire him.
Earlier I meant to applaud the average police of first world states, but yea 3rd world is pretty messed up(heard a lot horrific and retarded stories from China before they modernized), but it's not surprising for people that can hardly make a living and still need to put their lives on the front line.
For the rest of your argument I gotta admit you have a point and sounds rational even to a pro-police person like me. I'm not too fond of the idea of cops that failed horribly are still given another chance to become one again, chances they can repeat the same mistake. Though there's a few things I'd like to bring up is, imo a police job will always involves lives, this is the burden they carry and even if they messed up, as long as they tried close to their best to help and in an practical manner(due to ever lack of resources and budget), it's hard to really blame them. I mean we all remember when we're kids we've made a lot of mistakes in our class exams, even if we studied for weeks prior to it and read and answered every question carefully, mistakes still happen, and I see a police task not much different, except it much more critical and involves lives.
For American cops I think they're the one of the most professional people in the entire universe, even giving them credit for having balls of steel isn't enough when you know guns are a plague in the US.