You're not wrong.

This is what it can "appear" to be. Especially to the person suffering.

But we could also anthropomorphize cancer or diabetes or any other condition--even if they don't directly affect the brain. It's just not necessary.

A condition is a condition. It has no mental faculties to plot against you. Calling it cunning or evil is fine as a metaphor, but does little to accurately describe and treat the condition itself.