My brother, quite an intelligent person, attempted to do just that at least three times but no law enforcement agency would admit him (clean record). I am assuming this is because he made comments that to them seemed subversive in interviews.

How about as a taxpayer who funds the police, I have a say in how they operate. No need to become a cop.

How is this the solution? Wouldn't the selection process of any bureaucracy be designed specifically to 'weed out' people like this?

Yes, and that seems like a fairly likely reason that police agencies are by and large ossified in to this sort of behavior