I think it's much more of the fact you are clearly belittling the discrimination and societal hardship autistic people face. I mean, there's currently a mass movement to avoid science which ends up killing peoples children simply because these people are terrified of autism... And your response to them being autistic is "As long as you don't lie to me, it's all cool!"... really? What does that have to do with anything? This shows your complete lack of understanding of their hardships, and people are well versed in recognizing these signs and basically knowing right off the bat that you won't really be accepting of them. It's basically like if you were talking about gay people and the second someone tells you they are gay, you say "As long as you don't hit on me, we are all good!" that's a homophobic tell, and people would rather just cut it off there than hoping you aren't the worst of the worst.