I just watched a show on possible ice age effects from global warming from the oceans becoming desalanized, and the scientist said if this is the case, the earth will only sustain 2 Billion vs. the 8 billion now. (He literally said "6 billion will have to go!) It makes sense that if unbelieving people look at things without feeling any moral consequences (blowing them off as dated, fantasy, etc., sound familiar?) they would feel good about killing off people for the "greater good."