In other words, humanities and social sciences, much more than biological and mathematical sciences, challenge you to imagine the world though the eyes of others. And this exercise in imagination undercuts religious dogma far more effectively than any science lesson can.
...both the Humanities and the Social Sciences see dramatic declines in attendance and even more in religious beliefs. Now, this might simply be because they were more religious to start with - but then, so were those who went into education. So I suspect that broadening world views is the major reason these students lose their faith - a conclusion also suggested by the fact that, in the Spirituality in Higher Education Study, participation in a "study abroad program" also created increased skepticism about religion.