We would like to sell this property as a rental, but knowing the behavior of the occupants, they probably won't be willing to allow interior access for review by an agent or buyer. 

Evictions for anything different than non payment of rent a hard but not impossible and you don't know yet how far his behavior will go.

There was no law stating that I had to do that  (show ID)"True enough sir - but in a civilized society gracious behavior should be a standard operating procedure.  

Ask for the tenant/prospective tenant to describe the animal's behavior and personality in their own words.

The reality is you cannot force people to live how you want them to live but you shouldn't make a habit of tolerating the behavior when its a violation of the lease.

No, I don't enjoy it, it is the obligation of all members to call out bad advice, illegal or unethical behavior......and most of us do.We recently had a 7 page thread that was taken down due to suggestions that fell outside the line of ethics and even into illegal operations as well as with a heavy "under the radar" marketing aspect.

People's past behavior is the best prediction of how they will act in the future. 

I'm using this data to build logic to determine when a buyer is a hot lead based on their behavior.

You run a rental property business which puts you in an excellent position to improve the lives of people, the planet AND to build wealth, all without engaging in value-less behaviors.

There is NO justification for what you did, and to continue trying to justify bad behavior just makes you look worse.