Because it's easy to construct angels and demons in one's mind, about anything. It polarizes the mind into fear and desire, forcing forcing a person to continuously oscillate between extremes. It makes it seem like there are always only two choices, when in reality, there are many, if not infinite.

Also, there are always going to be some people who understand the machine better than the machine understands itself. Even if it means taking those gigantic tables of probabilities and abstracting over them to form some kind of representational language that can be used to predict complex non-deterministic machine behavior (similar to how we already try to predict non-deterministic behavior, or not) in complex systems.

As a corollary, I would argue that machines have already modified humans. They affect the way we think and reason. They are an integral part of our life and the machine abstraction can be projected onto that which it does not describe completely (in which, the technology that exists now can not construct the technology we envision). We program machines, machines program us. This seems obvious.