To expand on that in more recent times, when a new religion was made, it was usually persecuted with several of it's members often being killed. This leads to the religion creating a rule or a norm in which people reproduce more often. Christianity encouraged its followers to be fruitful and reproduce. This means, of course, that gay people are a threat to the survival of the religion. So, they make something up that says they are bad. The religion continues on for 1-3 thousand years and the followers are still following these norms and listening to these rules.
To expand on that in more recent times, when a new religion was made, it was usually persecuted with several of it's members often being killed. This leads to the religion creating a rule or a norm in which people reproduce more often. Christianity encouraged its followers to be fruitful and reproduce. This means, of course, that gay people are a threat to the survival of the religion. So, they make something up that says they are bad. The religion continues on for 1-3 thousand years and the followers are still following these norms and listening to these rules.