Timothy George's article is now online, providing occasion to ammend the "Staying Protestant" list:
7. Matthew 3:9. Self-explanatory, and perhaps the best one so far. How did I miss this?
8. Acts 7:48-49. Stephen's unique take on the Old Testament in Acts 7 has a very "Protestant" flavor, a reminder that there is room in the Kingdom for both people of temple and tent.
Also recall Edward T. Oakes' intriguing suggestion.
update: The search is finally over. Thanks to Joe's comment below, the perfect verse for staying Protestant - and I mean perfect - has been cited to provide all justification (mixed, albeit, with painful regret) for that peculiar northern compulsion:
9. 1 Kings 12:23-24. Said Joe, "Even if one were to grant that the Roman Church is the church, we need not conclude the Reformation was unfounded. Elijah was a mighty prophet in the northern kingdom, and even there God reserved 7K who did not bow the knee to Baal. Perhaps some of us, like Elijah, are called to the North."
I love being outdone.