My immediate thought is that "going autistic" could also be seen as insulating yourself from common social engineering attacks.
A straight male is fairly easily exploited by an attractive female fluttering her eyelashes at him. Autistic mode could be seen as a defense against this kind of attack, by being oblivious to the flirting and missing the sexual signalling completely.
One could even argue that social values like enforced monogamy and the taboo of adultery simulate this "autistic" behavior in neurotypical individuals. These moral values could have been naturally selected for in cultural evolution to protect social groups from infiltration from malicious outsiders.
