You can't even teach calculus to some people to the point where they can pass a class. Some people in programming classes can't even submit homework that compiles.
Calculus classes are more passable than programming classes, and the claim you're making is just pulled out of your hat, made in such a way that you could never be found wrong, because no matter what you could just say you're not taking the right approach.
Like any other skill, programming comes more easily to some than others, but with the right approach can be acquired by anyone.