I can't address such abstract questions as "mankind's survival", but I do know Leftist organizations have been responsible for around 100,000,000 deaths, give or take, and that's not even counting the abortions brought to you by that same school of thought.
BTW, isn't "mankind" a sexist term? Why haven't any of them corrected the OP? Oh, it's not quite dark yet. The DU Feminazis are still hanging from the attic rafters in slumber.