I don't accept the postulate that there is a way God could undeniably prove they were actually God. It could just be an extremely powerful yet still mortal and physical being, perhaps some advanced alien, that has come down to fool humanity. Whether it is or not is beside the issue, the possibility is there.
Since my senses are fallible, I have to assume that they can be tricked, so nothing I could witness would be something I could point to and undeniably state that it's the cause of an omnipotent, omniscient, supernatural being.
So even if I'm wrong, I would deny this supposed God's omniscience, and disagree with their claim that homosexuality is wrong.
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Goodnight Austin Texas, wherever you are!