I had this once. Again it was an elderly man. He would throw handfuls of dry dog food over the fence as he walked past. One day I lay in wait at the time he usually passed and had a go at him. He said he did it to stop the dogs being aggressive! (They are GSDs so bark when anyone enters their territory - and anything they can see is their territory!)
I pointed out to him that he was making them aggressive to anyone who dared walk past and NOT feed them.
They weren't aggressive.
2 had special diets, which his - probably cheap - food would not cater for.
His response was that they are dogs and can eat anything, so I asked him what the salt content of his food was, as my boy had heart disease and had to have a low sodium diet. Also, did the food have the additives BHA/BHT as one of my others reacted to this and became hyperactive - AND WOULD BITE IF APPROACHED when high on it.
So his attempt at making my non-aggressive dogs, to stop being aggressive was killing one and making one aggressive 
I asked if he also gave the children at the school sweets through the fence, at which point he wandered off muttering about mad bints.
Didn't do it again though!
Did you confront this man? if so, what did he say?