Guys, cut the foolishness.
The original question was whether or not it mattered that one believed something that wasn't true. The answer is obvious. Of course it matters, especially given the weight that God gives to truth (the weight of Himself), and His abhorrence of untruth, and His disdain for ignorance.
Then the question turned to WHY one would WANT to believe an untruth, and there can be only one answer. Sin. Men love darkness rather than light, because their deeds are evil. There is not one man exempt from that condition. To say otherwise is to say you have no sin. (And herein is a cardinal difference between Calvinists and Noncalvinists. Noncalvinists do not believe the love of darkness is in them.)
Now, nowhere did I say that a Noncalvinist is necessarily unsaved. BUT, he is saved despite his Arminianism, not because of it, and some carry their error to the grave. But it is error, and more die in their sin because of it than are saved despite it. It is NOT the Gospel of Christ.