Ha, ha, one of my dog training clients used this same technique with his grouchy neighbor. 14 days later, he was OK and had quit his nasty remarks. People are trainable, as long as they don't know they are being trained. Once I complimented my teen daughter for putting away the laundry, (free shaping!). Her response: "Yes mom, click!"
Deja, GSD, sable WL, female, born 11 / 2013
Cam, Rough Collie, sable, male, born 8/2015