Amid the hustle, bustle and period melodrama of Downton Abbey this year, one thread stands out as particularly problematic: the rape of lady’s maid Anna (Joanne Froggatt). What makes her assault so difficult isn’t the crime itself — although it felt as out of place in the normally placid series as Mr. Pamuk’s death-by-seduction in the first season — but its aftermath, and the character the show ha