I find it a lot easier to understand a Catholic who doesn't believe in God than an atheist who does. The self-identified Catholic considers himself a member of a cultural grouping, with social functions, various shared rituals and customs, etc. The beliefs are mostly irrelevant.

And I'm not too troubled by that. It's slightly inconsistent, but no more so than many other things we commonly do, and I think it highlights some of the reasons religion appears to persist, and makes it clearer that despite our first inclination, treating a religion as equivalent to its dogma is missing most of the picture.