1. The general rule that English speakers use to choose a gendered pronoun depends on what the speaker believes a person's gender is, not what the referent prefers or believes. You don't get to choose their words for them.
2. You should clearly be offended if someone uses the opposite gender that they believe you to be. (If someone thinks you're male but refers to you as female).
3. It's not at all clear whether or not you should be offended when someone uses the opposite gender that you believe yourself to be, even if they know what you prefer. (If you believe you're male, but they believe you're female). The fact that I'm neutral or uncertain in this case might be why you couldn't pin down my argument.