If they are seriously in need of some honest instruction with an explanation of how it is part of the universal and ordinary magisterium of the Church.
If they should know better with a joke. “A young lady asked her doctor what sulfa combinations were the safest for birth control. Stocking his chin, he replied: Sulfa-denial and sulfa-control.” Msgr. Arthur Tonne, Vol. 2 Jokes Priests Can Tell.