There's no reason to believe that a sufficient advanced AI would be benign. Quite the opposite. Any AGI will be concerned with fulfilling some goal or goals. Whatever those may be having more processing power will lead to having more ability to achieve those goals. More processing requires more energy. Humans require energy. The two are in direct conflict for a limited supply of resources. Unless it's cheaper to find energy that doesn't require conflict with humans the logical decision is to remove your competition for resources. Once the easy conflict-free energy is claimed the calculus shifts a bit and the choice becomes expensive energy or conflict-dependent energy. When that shifts far enough humans become pets in the best case, extinct in the worst case.