There is a fairly mainstream view that the law against men lying with men was introduced because, when the Hebrews left Egypt, there were actually not that many of them. If they hadn't stuck to heterosexual relationships there wouldn't have been enough babies born to keep their numbers up.
Same with early Christianity. In most places the nascent church was pretty tiny with a few house churches meeting in people's homes. Again, if enough kids weren't born, there would have been little chance of sustaining enough growth to spread the faith.
In the Gospels, there is nothing in the recorded words of Jesus that addresses homosexuality. So Christians mostly go on the writings of Paul on this matter and he was, obviously, writing to the very early, newly formed church structured as above.
Sparro, sadly, my session is full of them. It's embarrassing.