Why would anyone bother to pull a stunt in a primary that has only 20 pledged delegates and is not great territory for Sanders? Seems like an odd place for a "conspiracy".
Then why did this happen? Also yes every person that is in an election should be on the ballot and if this happened to Clinton i would want her on as well.
Perhaps because it was an error and nothing nefarious? A stunt over a very limited amount of pledged delegates makes no sense. If this was New York or California then maybe it would be suspect, but not District of Columbia.