I can see that you did not mean anything offensive by it. However, I have had similar things happening to me (misdiagnosis of autism so my parents did not have to take responsibility for tramuatising me) and I might have responded similarly.
When someone imposes a diagnosis on you that is wrong and does it for selfish reasons, when you are a child, it is very harmful. It hurts your feeling of self worth to the core and makes you constantly question yourself and who you are. It takes a lot of strength to stop the selfdoubt and finally conclude that you do not have autism and that what you feel and think is correct and not what you have been told all your life by the people you were supposed to be able to trust. That is really a very difficult thing to do, because the anxiety that something is “wrong” with you after all is always there. It takes courage.
If you have been struggling with questioning yourself in this way and if you state that you are not autistic after all, then it is difficult to deal with a response suggesting that you might be wrong. That is almost painful.
I know that you did not mean it that way. There is no way you could have known if this is something you have no experience with. Also, I cannot say something about why someone else responds in a certain way. I might be wrong about that. However, when I read your question, I immediately got quite triggered as well. I guess I just wanted to explain where a response like this can come from in some cases.
I think you have to be evil to become a billionaire. Nobody by themselves contributes something to society that is worth billions. So they are taking more than they contribute and are apparently willing to do so and disadvantage other people. This is evil. That is why there are no good billionaires.
Also, if by some extreme coincidence you become a billionaire by accident and if you are a good person, you would give it away for the benefit of society. So then you would not be a billionaire anymore.