Invalidating your life experience and labelling you with the feelings the other person thinks you ought to have... gah. No wonder you were furious. I'm glad you can feel that something positive comes out of the anger, but I hate that you had this experience.

This probably won't help at all, but you might think of it in these terms: the person clearly doesn't know you at all. So what they think is a figment of their imagination. Transference, really. Nothing to do with you, and so they and their opinions don't matter. I know that's easy for me to say, and I've been at the receiving end of other people ascribing feelings to me so many times that I know it's not easy to shrug off.