To add to what The Mysterious said, it's like if you followed a politician or president or whatever and they had built your support/interest by being really for issues that you believed in and then one day was like "Eh, fuck it. Just joking." I'm not saying the new TCM CD won't be great still and I listen to loads of secular/atheist/agnostic bands but I think it's 100% understandable if someone were to have an issue with him losing his faith.
And yes "God isn't a requirement for a happy life." but it is disheartening to see more and more people give it up. I try to respect everyone's unique beliefs but when it comes down to it, I see atheism as a way of life that sees there is no hope. ("Know Hope"? -_-) Like the religious/spiritual are the ones who are hopeful/positive and the atheists are often cynical.