It's not that it's lag in the usual way you get lag which is why they don't realise. It runs flawlessly for them because their connection is poor and the game is compensating for that which means those with a better connection get fucked over by opponents being bullet-sponges and also by having your movements out of sync with the enemies screen. So on your screen you escaped behind cover but on their screen you're stood still like a lemon because your actions haven't been transferred quickly enough from the host to their connection.
It's infuriating!
Treyarch trying to balance the game so these donkeys with poor connections are compensated for because they'd get completely owned otherwise, but with this they bring detriment to those with decent connections by bringing their experience down!
These idiots that say the game runs fine for them need to realise that it's not lag, it's lag-compensation.