While I agree that programming and math are different fields, I have trouble believing that a great programmer would be unable to get through calculus (and vice-versa).

Another reason for the association of programming with math is that the two fields have an incredible intersection. As a math major, I took a lot of math courses that cross-listed with computer science or had a heavily computational component. Anyone who has taken numerical analysis or worked through the last third of the advanced algorithms book has seen the extent of this relationship.

There are huge classes of differential equations that can't be solved without programming. Same for optimization problems (the simplex method has to be one of the greatest intersections of math and programming in history). Simulation (and not just brain-dead random number slamming) has made it possible to solve probability problems that were unsolvable a couple of decades ago.

So while I tend to view math as domain knowledge for a programmer - ie., an area where you apply programming (like chemistry, real estate, acounting...), the relationship seems deeper and more natural.