I don't totally disagree that they "just make more". But how is democracy going to stop them from making more?
The countries that produce terrorists have, for the most part, given their people no real choices in life. If perhaps some of these young men were given the opportunity to make something of themselves, or to even simply have a productive job, maybe they would want to live. Education is the real problem, and countries that mandate schools that teach only the Koran (sitting on the floor, rocking and learning to hate the West), create wave after wave of monsters who think killing infidels is noble. It is worth a shot, since whatever they have been doing does not seem to encourage respect for human life. The only other answer is carpet bombing, and I don't think that would be well received. ;)