Not much advice here but I’d say save all those messages this guy is sending and turn them over as evidence of harassment if you can.  

You may also want to add a harassment complaint to reduce the stress. 

I would have liked to be even 25% partners on the buy and holds I helped acquire and rehabbed to rent status .. but that realtor got into his head .. when I confronted her on it , she accused me of sexually harassing her .. ( she’s a piece of work .. and she’s doesn’t like men ..as in , she’s in a relationship with a woman .. even if she didn’t look like a man ) I would never sexually harass anyone  ! 

It just is kind of harassing and I'm not sure what to do at this point.

The neighbor on one side has been harassing them for some time, shouting homophobic slurs and insults, throwing trash in their yard and such. 

There is such a thing as phone harassment.

I also found other AirBnB units in the same neighborhood Guess it was too successful as a neighbor started to complain, harassed my tenants and alerted the HOA.

Yes,  You start harassing the Borrower and treating the loan like it is in default and you can find yourself in hot water.  

You don't want to harass them, particularly if you call so soon and they haven't seen your card.

The Fair Employment and Housing Act (FEHA) prohibits harassment and discrimination in employment because of race, color, religion, sex, gender, gender identity, gender expression, sexual orientation, marital status, national origin, ancestry, mental and physical disability, medical condition, age, pregnancy, denial of ... www.dfeh.ca.gov/Publications_FEHADescr.htm Even though the above definition does not specifically state this applies to housing the California Department of Fair Employment and Housing brochure below says as much. http://www.dfeh.ca.gov/res/docs/Publications/DFEH-157H.pdf And yes I agree - bad information is worse than no information.