These misanthropic beliefs are primarily limited to elites, who have become so decadent as to hate mankind. You have Prince Phillip, the Duke of Edinburough saying "If I were reincarnated I would wish to be returned to earth as a killer virus to lower human population levels." Also some of the more fanatical environmental groups are less about loving the environment than hating people. You also see similar sentiments expressed in modern architecture -- the idea that architecture shouldn't be beautiful or comfortable because people should be uncomfortable, etc, as in the famous debate between Christopher Alexander and Peter Eisenman. This idea of hating your own group or even hating all mankind is basically the extreme end of modern decadence, a luxury primarily afforded to a subset of people in the wealthiest western nations. Fortunately, it is not shared by the bulk of humanity, or even by ordinary blue collar people in wealthy nations.