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Anything can sound ridiculous if you use the right words for it.
This "space god" business is exactly the same tactic the religious Right uses on evolution. "Do you realize how ridiculous it sounds that we used to be monkeys? If we used to be monkeys, why are there still monkeys?"
Despite never actually having seen one ourselves, we trust some scientists we've never met that there are millions of little creatures swimming around in our bodies, some of them good and some of them bad.
This is generally a belief. Why? Because you probably haven't actually seen them. You're trusting the authority of someone else that they're there. They would sound, if we'd never heard of them before, ridiculous. And yet being ridiculous is not proof that something is untrue.
Of course you can't prove a negative. But if my belief system isn't harming you in any way, the burden of proof is on you to actually come up with some real evidence that it's a problem. If you want to say that religious extremists are a problem, I think there's ample evidence that you could provide for that. But where's the proof, Bill, that moderates are doing any harm at all?
If you're going to argue that the chief problem with religion is that religious people are not rational, it would behoove you to approach the problem in a rational way yourself.