I try to focus on the policy or behavior, not the party or ideology promoting it.

Since he is your cousin, you might want to consider giving him an opportunity to correct his behavior.

In addition, the owner of the home must not own more than three single-family homes.3) They are unable to provide sufficient documentation, such as the emotional support animal letter, that verifies the ESA is necessary for their health and well-being.4) The tenant provides fraudulent documentation attesting to their need for an emotional support animal (usually a fake emotional support animal letter).5) The landlord can demonstrate that making accommodations for an ESA would impose undue financial burden or logistical burden. 6) The animal is destructive to the property or displays threatening behaviors that could put other tenants or yourself at risk.7) The size or nature of the animal makes it impossible to house safely or humanely.

Professional and competent behavior is required to run a business."

I would then follow up with the upstairs tenant and let them know that I had issued the offending tenant a written warning about the behavior.

Have an "instagrammable space" like a mural on the wall with your hashtag prominently displayed. 

just read a great article in WSJ about Professor Daniel Kahneman who passed away 2 days ago, he and Amos Teversky invented the modern field of behavioral economics.

this is my Aviation partners business up in Oregon city  relevantbuildings.com/check it out his are all approved in Oregon .. but these are not cheap park model MH from MH manufacturers.. he has units on display his yard is between Canby and OC on hwy 99  on the river side of the road.. 

I'm not sure how old your "oldest son" is that can hear them arguing, but if he's older and is ok with recording them on his phone (if he can hear it, he should likely record it), then you'd have some sort of proof of threatening behavior and lease violation in case you call the police. 

This prohibition includes but is not limited to, loud noises, loud music, noxious or unpleasant orders and disruptive behavior or actions.