Your landlord friend isn't as much "desensitized" as he is "enlightened" to human behavior. 

Nuisance include animals in public areas who are not under the complete physical control of a responsible human companion and on a hand-held leash of no more than six feet in length or in an animal carrier."

An appetizer tray (real or faux food, depending on your needs), designer furniture, and fresh paint make all the difference.2.APPEAL TO BASIC HUMAN NEEDS: SHELTER, FOOD, & A SENSE OF BELONGINGThis doesn't mean we can set a bottle of wine on the counter and wait for the house-selling genie to work his magic.

(We see a lot of clients do this like these two, and if I were in your situation this is what I'd do, but that's only because I'm only so fond of other humans and don't want roommates.)

These are things that human beings excel at.

This is just human nature though, as the tenants are home after work and notice things not working at those times. 

As for self-growth in human relations and productivity, The 7 Habits of Highly Effective People by Stephen Covey is excellent.

Her real estate agent tried to explain it away, saying it's human error and those things happen.  

If the Seller is essentially the bank, I worry about human error.

There's definitely a human (emotional) element to this scenario, but from those more experienced...are most sellers in this position open to further questions for understanding the property or do they tend to be a "you get one shot, make it quick" kind of thing?