There have been, and are, many mass killings of minority groups and of enemy populations and conscripted soldiers at war. If we cure death and diseases, this will become the biggest cause of death and suffering in the world. It's important and we'll have to deal with it eventually.

The AI under discussion not just won't solve the problem, it would (I contend) become a singleton and prevent me from building another AI that does solve the problem. (If it chooses not to become a singleton, it will quickly be supplanted by an AI that does try to become one.)