A basic Crowhill political principle is that some people have to have power to create and maintain a successful society, but you can never trust anyone with power. Power will corrupt. It’s a matter of when, not if.
It looks like the Brits are getting another example of this principle. Daniel Morgan murder report: the ‘devastating’ verdict for Scotland Yard
Police will become corrupt. It’s inevitable. It doesn’t matter how many nice people become policemen, or how many good, self-sacrificing things policemen do. They’ll eventually cover for one another, lie, hide evidence, take bribes, etc., unless there’s a strong force to keep them in line.
Which is, of course, the secret to handing out power. You give group A power, but you give group B the power to kick them back in line.
“Defund the police” is a childish reaction. If you believe there’s corruption in the police department (and of course there is), the slogan should be “audit the police,” or “investigate the police,” or “double the funding for public defenders,” or something along those lines.