I think you could take practically any industry and play out a scenario in which this will have a major effect on that industry and it's employees. 

I feel they are over reaching and out of step with modern STR practices.

You're doing the right thing by getting practice in, analyzing deals, and building your network.

What are the best practices and methods to protect yourself as a landlord?

@Eric Seo.

The new document https://www.hud.gov/sites/dfiles/PA/documents/HUDAsstAnimalNC1-28-2020.pdf spells out best practices for property managers and landlords with respect to assistance animal requests.I hope this will provide you with more info on how to determine if the animal is qualified and how to screen tenants Cheers, Yuriy 

What is best practice for dealing appropriately with tenants?

The principle holds that 10,000 hours of "deliberate practice" are needed to become world-class in any field.

But practically, it is very doubtful it would be with it to try and force the sale....could be months and many thousands in legal fees to get in front of a judge. 

I practiced law for twenty years in the U.S.