(Seemingly) any @e data selector that is not "type" fails to filter results; command instead ignores specified entity data.
Confirmed in 14w31a as well, though I do not see that snapshot listed as a version option.
Steps to reproduce:
1. Summon villager & zombie in hard mode.
2. Let zombie convert villager into zombie.
3. Use /kill @e[type=Zombie,IsVillager=0]
4. Both zombies die instead of only the non-villager zombie.
Also:
1. Summon villagers of multiple professions.
2. /tp @e[type=Villager,Profession=1] @p
3. All villagers are teleported to the player instead of only the single profession.
You cannot use NBT tags in the selector.
You want to do
but that's not possible, see MC-46336