Hmmm….I don’t think it is a “sin” to believe a fact (if something is indeed a proven fact like the earth is round). I don’t get the presupposition here! Believing a fact, in my opinion, has nothing to do with being a Christian, unless the Christian “uses” the fact to do “un-Christian” things. In this case, if the fact is true, then it really has nothing to do with being a Christian. A fact is a fact. But if the Christian says because this is true, I will treat someone like an inferior human being, or will treat someone unjustly, then that is where the problem lies, I believe. I believe in micro-evolution and some Christians I’ve met think that is a sin, even though there is evidence for it (not macro-evolution).