The EVIL are not entirely without weak points. Like true kittens they are repelled by water, distracted by yarnballs and catnip toys and made docile by milk. This does not, however, make them any less lethal.
It was revealed that the EVIL were bred by Satan, during the drunken party the satanic cult of Wispydale held for him. Any questions about the incident were answered by a "I do not want to talk about it." He left the cult in charge of feeding the kittens a bowl of milk every night, on pain of their destruction by the kittens.
It turned out that the kittens went on their rampage due to their caretakers giving them soy milk instead of true milk.