I don't think many associate intellectual capability with evil. What many do, however, is associate serious risk with living alongside vastly more intelligent entities. Especially if those entities are not aligned with us.

> Why do people automatically associate intellectual capability with evil?.

No intellectual capability, but non-human, inherently amoral intellectual capability that has already been proven act in hard-to-predict, illegal, and unethical ways. I think that's a very rational thing to be afraid of.