As someone who writes fantasy set in nonexistent worlds, I spend a fair amount of time contemplating religion and why people believe what they do. Making up a world is a little like buying an empty house; once you know the floor plan and the size of the rooms, you need to be sure you have enough— and the right kind— of furniture. Your empty world needs not only people but customs, language, history, and, in most cases, religions, or it's not going to be very interesting.
On a purely personal level, I'm basically an agnostic. I'm not convinced either way that there is (or is not) any kind of Supreme Being. I am convinced the Bible isn't the divine word, and I certainly don't believe in the creation myth. I'm just not willing to say unequivocally and without any doubt that if we can't see it, it's not there.
Actually, I suppose one reason I like writing fantasy is when I do, I get to decide. If I create a primitive culture in which people worship a pantheon of pagan gods, I can decide that in my story those gods will be real— or not. Gods with real powers can make for a good story. But so can a situation where people act from a firm belief, no matter how mistaken, in some specific god.
And of course, in real life, many people use religion as an excuse to treat one set of people (women, gays, non-believers, etc.) very unfairly. But no matter how unfair (and disgusting) that is, neither is is fair to tar all religious people with an intolerant brush because some of them use their religion as a Get-Out-of-the-Bill-of-Rights Card.
To apply a spec fic quotation, here are words to live by from the late, great Kurt Vonnegut:
“Hello, babies. Welcome to Earth. It’s hot in the summer and cold in the winter. It’s round and wet and crowded. At the outside, babies, you’ve got about a hundred years here. There’s only one rule that I know of, babies — ‘God damn it, you’ve got to be kind.’ ”
For a more mainstream appeal, another the person whose sentiments I'd like to invoke is Rodney King. To quote him, "Can we all get along? . . . I mean, we’re all stuck here for a while. Let’s try to work it out."
For a start, let's try to stop stores from playing those dreadful Musak versions of Christmas carols. . .