Growing up Catholic, it seemed there were literally hundreds of commandments, including "be fruitful and multiply". Transgender and homosexual people don't multiply very often, therefore the church considers them sinful. But then, using any form of contraception goes against the teachings of the church, and is therefore sinful. So, it does not matter if you are gay, trans, or straight, if you have intercourse for any purpose other than breeding, you have sinned against God, according to them. The Catholic church is not the only institution that believes this dogma. Go to almost any church, and you will know this to be true.