People cannot help being born and being there, but the concept of overpopulation can easily suggest that part of the people do not really deserve to be there, or that they should not exist. From there, it is only another step to hating part of the human race and to feel justified in wiping that part out (or at least subject people to compulsory sterilization). If people believe that each human being has a right to be there and enjoy life, there cannot be "overpopulation".