GPs probably have a basic understanding of the presentation of your common ASD on average (they do have to attend various seminars for updated information after all), but it's probably not wise to take their opinion as anything solid unless they give you valid reasons for why.
To add:
It's best to show them why you think what you do, with evidence. If you can't talk much, have an advocate do it or write it out (not too much with the writing though in my opinion. Just facts). Probably self-evident, but many people don't question professionals.