Because Protestantism and Catholicism have developed together in the past 500 years (not to mention historic antecedents to the Protestant Reformation), Protestantism has a finely-honed view of what’s wrong with Roman Catholicism.
By contrast, Eastern Orthodoxy has been an outlier to this process. So how should Protestants view Eastern Orthodoxy? Is it just as bad as Roman Catholicism? A little bit better? A little bit worse? A whole lot better? A whole lot worse?
Here are two simple ways of answering that question:
1. I’ve read Orthodox churchmen who classify Protestant theology, or some variant thereof (e.g. Reformed theology) as heretical. But if Protestant theology is heretical by Orthodox standards, then Orthodox theology is heretical by Protestant standards.
(I’m confining my comparison to the points where they conflict, and not across the board.)
So we can simply take the Orthodox viewpoint as a proximate reference point, then reverse the logic. If our “heresies” are their orthodoxies, then what they take to be their corresponding orthodoxies are heretical from our own vantage point.
2. A minor error, or even a minor truth, can become a major error if it is elevated to the status of an all-important truth. Take Seventh-Day Adventism. The day on which we celebrate the Sabbath is of no essential significance. Its importance is strictly symbolic.
And even in that respect it doesn’t have quite the same significance it had in the 1C. At a time when the Jewish Sabbath was the frame of reference, a shift from the seventh day of the week to the first day of the week was highly significant.
But the very effect of that shift over time makes that particular the day of the week loses its original significance precisely because we no longer use the Jewish calendar as our frame of reference. We’re not consciously contrasting the first day of the week with the seventh. By making Sunday our Sabbath, Monday becomes the first day of the week. By shifting one day, the entire sequence is shifted by a day.
(Of course, we can still preach on the original significance of the Christian calendar.)
The problem is not so much that Seventh-Day Adventists celebrate the Sabbath on the “wrong” day. The larger problem is the way they turn this into an all-important issue. Indeed, even if they happened to celebrate the Sabbath on the “right” day, they would still be gravely wrong for hyping the significance of this penny-ante issue.
Likewise, consider the theological priorities of the Eastern Orthodox. What do they consider all-important? And compare that with the theological priorities of the Bible.