I can believe it. Back in my young stupid hippie days, I fell in with someone who used this same technique. It's very effective against those who are emotionally fragile, and it has the added benefit of spiraling your self esteem right down in the crapper, which makes you even more susceptible to manipulation.
If my best friend in the world ruthlessly criticises me as a means of saving his own life, it’s not gonna bother me that much. Maybe I’m missing something about this technique, but it seems like it wouldn’t be effective if you knew what the game was.