Religion (and thoughtful people) really should give way to science. Being trans is a matter of brain chemistry -- not sexual deviance, mental illness, or mortal sin:
So you have someone who by every measure discussed, from sex chromosomes to phenotype, is Sex A, but who insists that they have always felt like they are Sex B. What’s up in the sexually dimorphic brain regions? A number of studies report the brain bears a close resemblance to Sex B. And this shouldn’t seem surprising—we are determined by our brains, we are our brains, regardless of our pattern of facial hair, the thickness of our larynx, or what the landscape is like between our legs.
In other words, it’s not that transgendered individuals think they are a different gender than they actually are. It’s that they’ve had the profoundly crappy luck to be stuck with bodies that are a different gender from who they actually are.