“Religion” doesn’t believe anything. Religion is a deeply ingrained pattern of human behaviors stemming from deep awareness of the stark beauty and mystery of reality, and is not primarily about belief or disbelief.

Some religious groups promote belief in unbelievable things however. Some religious groups promote nothing but appreciation, reverence, love, and well-being.

If you are going to be scientific you should ask why it is that homosexuality is almost universally discouraged or condemned in human society. Homosexuality is natural, yes; but disapproval of homosexuality is also natural, and exists for reasons.