That’s where I take it from.
The Old Testament definitely condemns homosexuality, but since the Catholic Church lifted some precepts of the Mosaic law for Christians, the pope cannot simply make a reference to homosexuality in Mosaic law. A Catholic must understand that homosexuality is a perversion of natural law also, regardless of one dogmatic system or another, and homosexual act is a depraved act regardless of the faith of the doer, or lack thereof.