One of the reasons cops don't come across as 'Just a citizen doing the job'

to a lot of people:

Maryland was one of the first states to enact a “bill of rights” for its police, and other states followed. In other jurisdictions, those protections are a result of collective bargaining and embedded in negotiated contracts.
These laws and contracts do not protect the jobs of “bad cops” or officers unfit for duty. Nor do they afford police any greater rights than those possessed by other citizens; they simply reaffirm the existence of those rights in the unique context of the law enforcement community.

That's simply not true, unless Canterbury is using "the unique context of the law enforcement community" to mean "for people whose rights we actually respect and care about."
Let's take a look at Maryland's Law Enforcement Officer Bill of Rights that Canterbury mentions, and contrast the rights and procedures cops demand for themselves versus their habits in dealing with us.
It's not a nice comparison.  For instance
But for themselves, cops want the right to review evidence, especially in an age of omnipresent video cameras. In Los Angeles, cops are demanding the right to view videos of incidents before giving statements about them:

The proposed policy would also allow officers to have a union representative with them when they review the video – and they can exclude the LAPD investigator looking into their actions during that process.

Similarly, in Dallas, the police chief announced a new rule requiring officers to wait 72 hours before giving statements about use of force incidents so that they can review any videos or witness statements. That change just happened to follow an incident in which a video of a police officer shooting an unarmed man turned out to contradict the officer's immediate statement about the shooting.