How do I get my dad to accept my autism?

How do I get my dad to accept my autism? I still live at home, and I was diagnosed in my late teens. I've brought it up with him a few times, and he just dismisses it. Saying things like "but you don't seem autistic, you function well." I've even explained to him my specific symptoms, trying to show him that what I deal with is different from what "normal" people do through. He just says "Well I feel like that too. We're just introverts, it runs in the family." Like, my guy, I have Fragile X Syndrome, a GENETIC DISORDER that causes autism. Where do you think I got that genetic disorder from??? What is it gonna take for him to take my (and probably our) struggles seriously? Do I just stop masking in front of him and see how he reacts? Or will he think I'm faking or making it look worse than it is? I mean I don't understand why he can't accept it, it's a known fact that this runs on both sides of our family.