In all but two instances over two years, Ianto has been shown as being totally in control of this relationship. He initiates their encounters, he sets the boundaries, he plays and teases Jack but Jack doesn't play and tease Ianto. He puts Jack down in public. He's the one Jack turns to and asks if Jack deserves to be put down in public. That doesn't sound like a whipped puppy to me. That sounds more like the top dog.