I always use this saying and approach in dog training. I get really annoyed when people think they can train obedience by shouting and physical "corrections". For a start, they don't even understand English, for heaven's sake be reasonable!
But yeah, it's psychology 101 at the end of the day. Or just plain common sense. It even works its way into biblical text with "do unto others....". :)
I'm with you on using positive reinforcement for training dogs. Why use force on dogs when praise works so well?