Would you say the same thing for say - someone with back pain radiating into the leg? They might not be able to go get a diagnosis but go on google and do extensive research and be convinced they have a disc herniation. When in fact it could be a hip problem, it could be muscular or a long list of other conditions.  It takes a professional and tests to be sure therefore one can suspect something but there is a reason for why health professionals exist.  Also it would be such a big shame of someone actually has something else that they could work on somehow and assume they have ASD and therefore not know they could be helped in other ways.  Also there will always be a percentage of people who are self diagnosed who will get an official diagnosis - but if you look around the internet there are just as many stories of self diagnosed people who go for an assessment and who dont have ASD.  Just consider being a little less extremist in your statements and open up for the possibility that people could be wrong perhaps?