Given that most people who have Asperger's don't go around shouting it to the heavens, and that it isn't blindingly obvious upon meeting someone that they have it, my guess is that he had an idea of what he thought aspies were like, and confirmed his stereotype by eliminating from consideration anyone who didn't fit it. A bit like someone who says that "all lesbians are ugly" because if they meet any attractive women they assume they must be straight. Humans are very good at this sort of self-fulfilling prejudice.
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Do I look like a freaking people person?