Why shouldn't we require licensing for having children? Nobody would be "denied" having children, but you'd have to take courses, pass a mental competence test, waive your 4th amendment rights from time to time for surprise inspections and have 20,000 laws which dictate exactly how you may raise your children - laws which differ from county to county, state to state and pay a fee that has to be renewed from time to time (only several hundred dollars).
By poorly raising your child, he or she may turn out to be a menace to society. And if it saves just one life, isn't it worth it?
Tell me, why is this any different?
(stolen from my own comment over at Joe's)