he is wrong and he knows nothing of the eastern orthodox church or its history or beliefs
He certainly knows enough to disagree:
Prayer and devotion to saints...check.
Devotion to the Theotokos...check.
Episcopacy and apostolic succession...check.
Denial of substitutionary atonement...check.
Etc. Etc. Etc.
You'd best simply steer clear of theological arguments with these types. And don't waste your time on debating Scripture with them...they believe the "plain meaning" of Scripture is clear, and it happens to perfectly coincide with their interpretation of it. I banged my head against this brick wall last weekend in a disagreement with my Baptist father. "MY
authority is Scripture!" "No, your authority is your own personal interpretation of Scripture." And so on, in one big circle...