As I said in my other post, the act of exterminating all of these people would have deep psychological and spiritual consequences which would deform the nature of the emergent social order. A more intelligent, less emo solution would be to increase the intelligence of the population through more creative (and more realistic) means. Improve/restore religion, improve/restore education, etc. Encourage positive eugenics. Apply negative eugenics in a thoughtful, cautious way, where absolutely necessary and when it is unlikely to produce massive, unintended side effects (i.e, a spirit-crushing, cruel, paranoid social order used to killing people off according to an overly simplistic formula).