Someone otherwise smart told me recently that they believe in this nonsense because they have a relative with autism.
I didn't have the heart to ask them "what does that have to do with you suddenly believing that correlation means a causative link?!!?"
People love to believe that anecdotes are real data. It took thousands of years of human civilization before we actually figured out as a society that that isn't a good practice—and even now, most people still don't understand the concepts.
Try the term "the null hypothesis" on most people and see where it gets you.