Situations like these are so heartbreakingly frustrating, because there is no way to "win." I'm so glad you had other people in the group there to back you up. People still have such ignorant and narrow stereotypes of Autism; they think you can instantly "see" it in someone, and that someone who can communicate well or has any social skills (no matter how routinized) can't possibly be disabled. I don't know why I haven't run into as much resistance when I tell people as so many Autistics do; maybe I am just way worse at masking than I even realize, ha.