I got this idea from an off-hand remark made by a Buddhist monk in the book The Jew in the Lotus. But I've enlarged it quite a bit myself. Religion is like food. The basic rules common to all religions--treat others as you would like to be treated, pursue peace, love others--are the protein, the vitamins, and the nourishment. The myths and rituals are the seasonings that make the food a pleasure to eat. These differ far more than the nourishment, and are often culturally specific. Fundamentalism is like fast food. It puts the emphasis on taste at the expense of nourishment. Following the rituals and literally believing the myths become more important than being kind. And like fast food, it's addicting. Like all metaphors, it's not perfect. Taken to its logical conclusion, this metaphor suggests that atheists are either amoral or have no flavor in their lives. Since I have known many highly-moral atheists who have embraced life with happy enthusiasm, I know that's not true. But despite that failing, I think it's a good metaphor.