Despite fundies' hangups, this is why sex education is important:
A worried father confronted his daughter one night. "I don't like that new boyfriend, he's rough and common and bloody stupid with it."
"Oh no, Daddy," the daughter replied, "Fred's ever so clever, we've only been going out nine weeks and he's cured me of that illness I used to get once a month."
And yes, I know it's an old joke.
I don't spend my time trawling the net for or coming up with new ones, and what's an old joke to some people is new to many more.