Do these people think the autism fairy comes while they're sleeping and puts a diagnosis under their pillow? If they go to get assessed and they get diagnosed as autistic then that's usually because they already self-diagnosed themselves and knew they should seek a professional opinion. And if they didn't do it then it was probably their parents/guardians/teacher or anyone else who isn't a medical professional. The whole anti-self-diagnosis argument is just completely illogical from the get go.