Well, maybe someone who happens to be Jewish will turn out to be a blood thirsty dictator in the future and destroy the world, and that person would have never

Well, maybe someone who happens to be Jewish will turn out to be a blood thirsty dictator in the future and destroy the world, and that person would have never been born if his ancestors had been killed by the nazis. It's really far fetched, but one could argue lots of things by making assumptions about changing the past.