quoting from enders game (its a book), a species is incapable of choosing its own destruction. we might be prepared to die on an individual level, for the greater survival, but we are simply incapable of allowing extinction.
firstly, most of the cataclysm we know of wouldn't really wipe us out. say we all decide to nuke everyone else, we only have enough for cities, towns, and major population areas. people in deserts, very rural places, or out at see would be fine, and could repopulate. our knowledge and civilisation would die, but not our race.
putting the question a different way, if aliens came seeking to kill us and take our planet, should we let them? no because with any reason they are as or more flawed then we are.