I'm coming to realize this point. I only found out about being autistic back in May. Always just thought myself a little odd for sure but not autistic. Anyways i have found that when I bring it up a lot of people fall into a mix of 1,2, and 3.
I actually had an interaction with a potential romantic interest last week where everything was going great, until she asked why, in my studying psychology, did I want to focus on autism. Well I told her it was because I recently found out I was autistic myself. Conversation ground to a halt right there and I'm sure if I'd said "because I have an autistic relative" they probably would have thought it sweet.
I've decided that those close to me I'll be open about it. No choice really as they all know now. But strangers from here on out I'm not going to bring it up unless absolutely necessary.
It's tough when it's dealing with something in your head. If you have an injury, or physical disability people get that instantly no questions asked. But mental matters seem to weird Neurotypicals out, especially the ones that have never had any mental health problems themselves. I think a lot of the reaction is they simply don't know what to do. They can help someone with a broken leg by carrying their bags. Or helping a blind person down a flight of stairs. They don't realize that the best thing they could probably do for us, or any ND, is listen to what we have to say, nonjudgmentally.