I honestly don't understand what benefit there is to classifying the illness as evil, unless you're trying to sell a spiritual exorcism.
I can talk about my experiences with bipolar minds, and not on a self centered note. It's emotional deception, and the beholder is more tormented than those who've been tormented by them. The Manic side not only fills them with unbelievable grandiosity, but it makes people fall for them too. People love upbeat personalities that bring sunshine into their lives, It comes to a point where, in many cases in the bipolars eyes, the one who is most concerned for them needs to back off.
Suicide rates are high for the mentally ill, same with divorce, resentful children, failed friendships, promiscuity in ways that leaves a rather large sum of people left bleeding on the inside, sometimes all at once, extreme anger, extreme frustration, extreme jealousy, extreme fear, massive guilt and shame, mental illness can drive other people mad, but not as bad as the beholder. A friend of mine, his brother suffers from severe schizophrenia, for the past year or so, they guy was in the loony bin, terrified of the world. Hearing about it may sound amusing, but seeing it. Damn.
The world does not wish for this, nor do they choose to be around it. Someone goes nuts, and people get scared and are relieved with the one undergoing some mental psychosis is being wrapped and gagged and drugged up on a stretcher.
Is the illness evil ? Of course it is.