How do you like that, we actually agree about something. The fact that Luther could be wrong about something doesn't condemn Lutherans does it? From my perspective it only shows he was a fallible human like the rest of us.
“Fallible” in this context might well be the understatement of the year (and it’s only March).
Lutherans and Calvinists still believe that, though. It wasn't just a "Luther thing".
There are still people on the hard edge of the Reformation who will bitterly defend imputed righteousness over against the "Romish heresy of infused righteousness". If you need reinforcements from Opus Dei or the Swiss Guard to defend against the onslaught, just give me a call. ;-)