Gregory the Great did not say that sexual desire was in itself sinful but that in a fallen world it is disordered, as are our appetites for food and a lot of other things.
Unlike Buddhism, desires cannot in themselves be evil or sinful for Christians and Jews because desires were created by God. Since the Fall, however, they are disordered, big time.
When you find the Latin quote from Gregory that supports your claim, please post it. But don’t bother with quotes in translation from your anti-Catholic Cliffs Notes.