Yes, I too have experienced quite a bit of tenant bad behavior, but they are still my customers.

A home seller might be able to make a case that it is anti-competitive behavior for a group of licensed sales agents who control an overwhelming majority of the market to come together and agree that they are going to force a seller to agree to pay a commission not only to the agent representing the seller but also to the agent representing the buyer in order for the seller to be able to list his or her house on the MLS system that the agents control, which is also the system that sells the overwhelming majority of houses in the area. 

In addition, the house had a marijuana smell to it.I'm thinking it could be one of a few things:1) The tenants are concerned the owner is selling the house which means they might lose their tenancy and this was a way for them to disrupt the process to "keep them in the house"2) There was marijuana in the basement and they forgot the inspection was happening, and they didn't want to get caught with having contraband in the house as that would be means for eviction.3) There is actually somehow a flea infestation down in the basement (why the basement though when they have no dog and haven't reported it to the landlord?)

Is there some type of insurance that I can make a renter have or a contract agreement if they bring a dog that protects me if their dog were to bite someone on my property?

Behaviors can be learned to some extent. 

Typing up a letter or telling your dog doesn't count.

For example, the case of service dogs and emotional support animals. 

Same dog, different nametag.

He also came back after closing and broke every bit of plumbing by hitting or stomping on it and left his dog and cat locked inside with no food or water. 

When I deal with Bird Dogs I tell them what Zip Codes I want to find properties in, what specifically I am looking for in that property (duplex, SFR, Fire Damage, Vacant, etc .), and I make sure that they have checked and double checked the property address.