This is the same sort of arguement we get with pocket Jacks.
Think of it this way.
If you raise the pot their is a reason, therefore hammer the flop hard regardless, even if you have KK on an ace high board. To be honest, unless he's certain he has you outkicked eg AK, AA even and hes flat called behind you then really hes playin bad poker imo if he calls your continuation bet.
Ok on this occasion hes right but how many times is he going to poice you down to the river with AJ or AQ when you have better. Enough to make the play.
So bet the flop regardless. But obviously if he calls you have to make a tough call. Have you got a calling station or someone who has you read like a book?
The turn is yours to choose but you probably have to check it with KK and not give your chips away. Like everyone else says the always have it when i have KK. (and its usually Ax as well!)