Sounds to me like there's too much cultural inertia. They're not stupid, but admitting that sex causes pregnancy means admitting that Bob's wife cheated on him;

Sounds to me like there's too much cultural inertia. They're not stupid, but admitting that sex causes pregnancy means admitting that Bob's wife cheated on him; it means some poor desperate soul really did shag Ugly Betty; it means accepting responsibility for life-changing events that it's much more convenient to write off as "acts of god". The clincher is the fact that they've been informed of the link now, and still won't accept it. That's not stupidity, it's denial.