I see and then I agree. I guess the word that you used the threw me off into a tangent was actually "believe", no just "sin".
I absolutely agree that using the word "sin" instead of the phrases "immoral act" or "moral transgression" has practical value. The thing is I do think that the word is really overloaded with religious concepts and dogmatism and reclaiming it for secular purposes with an altered usage would be really hard. Despite that I do see the utility in trying to do so now.