The problem is that they made a typo. Previous CoDs had a Combat Knife. This one has a Pacifist Knife. That's why you can try to stab someone and the knife will pull you away from your oppenent. It's really hard to get a Pacifist to kill anything. Just wait until you start going for Bloodthirsties and the knife teleports you through the last guy just so that you can get shot in the back. It's loads of fun.
Remember when you were a kid and you would get the toy "army kit?" It came with a plastic canteen, a belt of some sort, fake grenades ... and a plastic K-bar.
Well, because there are so many children playing COD games, TA decided to issue everyone one of those rubber and plastic K-Bar knives.