Call of Duty Worlda at War is a videogame about the Second World War. It also happens to feature a minigame called Nazi Zombies.
The Mario franchise is a run and jump game prodomenantly. However, it still changes direction with various minigames such as trampolining, and it also has various off shoot games such as Mario Kart.
Just because a game, or for that matter, anything that fits into the media category changes direction, it doesn't mean that it is wrong.
In the case of World at War, Nazi Zombies made a welcome change from the war gameplay, and although the actual game itself came under alot of flack, the Nazi Zombie mode does not detract from the positive aspects of the game. If anything, it was a fun extra that most people, including the developers initially took ad a joke or novelty.
SVD, get over it. It is a game, and it's aim is to entertain, if it fails with you, why do you feel the need to tell everyone that they should hate it because it is not historically accurate, sounds insecure if you ask me...