I don't think you're missing anything. No matter how clever an AI, it cannot argue a rock into rolling uphill. If you are a rock to it's arguments, the AI cannot make you do anything. The only question is if your utility function is really immune to it's arguments or if you just think it is.

Utility functions are invulnerable to arguments in the same way that rocks are. It is the implementing agent that can be vulnerable to arguments (for better or for worse.)