You might fear a confrontation.

Unfortunately, instead of disengaging I somehow find myself drawn into a confrontation.  

And get this, when I confronted the neighbors about it, the husband bows his head and sleeks away; the wife tells me that since there was a big rain that washed debris from my yard to hers, and I was not there to clean it up, she didn't feel obligated to honor our agreement!  

@Mary Mitchell  Don't want to sound confrontational by any means.However, your general statement of your reply stating "some places require fridges, stoves, toilets and running water."

I was never confrontational or unkind. 

I'm not required to take a witness, but I typically do, in order to minimize confrontation and verify my story if I ever need it.

Why be confrontational at all?

And, she had other mail in there with her name on it - so we knew who had a rabbit snuck into her apartment.The problem was, we couldn't then confront her without letting her know the owner went through her garbage LOL. 

If confronted about this and their likelihood of liability, they may wish to settle. 

If the neighbors cross the line and do something physical / vandalize / confront , take swift legal action, but as an owner, just let them vent to you and calmly explain why you're not in the wrong.