The pastor does have a point, but I am not the “go to” guy for this one. You need a good scholar, not a hammer mechanic like me.
All I can tell you is that this is why Orthodox sometimes think of Roman Catholicism and Protestantism as two sides to the same coin. Augustine had much less of an impact on Holy Orthodoxy, Orthodox did not read him for centuries and when they finally did they dismissed his theories in light of the other Patristic Fathers of the east; his ideas about Original Sin, Depravity of Man and Predestination did not really penetrate the east.
Augustine was a huge influence on the Protestant reformers and later theologians. In fact, some things Augustine wrote about are not even accepted by the Roman Catholic church today. By conflating Romans/Galatians with Augustine you can build the seedbed to much of Protestant theological development.
