However if they have renters insurance, then their policy is 1st in line to cover the expense and legal defense.

If ever charged with a claim of discrimination, which is bound to happen if you are in the landlord business long enough (cynical, I know) you lose that critical defense of lack of knowledge once you have met face to face.

If you haven't already consulted both a Criminal Defense attorney and a Landlord/Tenant attorney, I would highly recommend doing so.

Very good practical points (and strong defense to any claim the tenant may make against you during the lease). 

While some breeds may have a genetic predisposition to certain kinds of aggression (towards other dogs, or in defense of their owners, for example), how the dog owner manages their dog and the individual temperament of the dog matter more than the breed.  

From a legal aspect, if something occurs such as fire, injury or worse, you have no legal defense.

Playing great financial defense with my bills.

The fact that they won't be able to provide them (and if they do provide pictures you have your time-stamped footage validating how it actually looked during the walk-through) will be enough to sway the judge to see the merit of your defense.  

If your dog bites, it's your fault, zero defense for it. 

No defense.