I think this "do nothing wrong" tendency has something to do with intragroup power dynamics. I've often seen it used as a cudgel to knock down others within a group and stop mild dissent even though everyone is on the same team. Usually the most prolific wielder of the "do nothing wrong" cudgel rises to a position of some authority in the group, after which the group fragments because the person is insufferable but unassailable due to their moral superiority.