Your argument does not rest on most cops being good cops, it stands if some cops are good cops. So why throw in an assertion you can't back up?
Care to back up that assertion?
"Unnecessary" and "dangerous" are quite different.
See, he's not holding himself to your standard of evidence. That would require mass mindreading, plus the ability to irrevocably demonstrate the authenticity of such.
Rather, he's backing up that statement with evidence in the reader's head, counting on most readers to reflect back on their life experience and see if his statement fits. He has faith that it will. In my case, it does: I agree. I'll even upvote him.