I think that religion, including all the mountains of stacks of books' worth of theology on the subject of sin, is a prime example of humans "messing" up. (An Anglican's recent heavy-handed use of the F-bomb, carpet-bombing with it so to speak, in order to show that he is "modern" and that we "don't understand him," has sort of spoiled it for me for the moment. He describes sin as The Human Propensity to Mess Things Up, except, because he's all "edgy" and determined to "shake us up," he doesn't say "Mess.")
But no. No. As soon as I wrote that I said to myself, It's not that simple. I can't describe tens of thousands of years of human activity in a handful of words. As it is so often, so also here, things are just much more complicated than that. Humans developed the way we did, and for tens of thousands of years that develop included religion. If one were to object to all of religion, one might as well object to our having skin, or eyes.
But to object to people continuing to be religious, and either being hopelessly ignorant of science and history, and/or to being maddeningly pretzel-logical in order to mask all of the things which science and history show us about how religion began and developed in roles in which it is no longer needed -- I think it's as reasonable to reject this continuation of religion as it is to reject the idea of people once again living in trees and living on whatever we can kill with sticks and rocks, as our ancestors did when religion began to motivate and organize them and to lead to things like cities.
We can honor what religion did. We can argue about when it ceased to be useful. We can point and facepalm and moan at those still caught up in it, shake our fists at them in frustration and mock them. To call it a sin would be to behave as disgracefully simplistically as -- a theologian. (Oooohhh, edgy! , not. It's about the speed of some of the FTB guys, if they want to use it I won't call plagiarism.)