That is the one of two main problems with the other choices i.e. the usual Mao, Stalin and Hitler (the other main problem is unintended consequences, which I shall touch on later).
The problem of convergent evolution stems from what happens in the wild, where in different environment (even different continents) different species of animal occupy the same niche. For instance, in the continent of Africa the main feline predator is the African Lion, in India it is the Tiger (apart from a small part called Gir where the Asiatic Lion holds sway), in South America it is the Jaguar, and in North America it is the Puma (although once upon a time the American Lion, much larger than the current Lion, ruled). In places like Australia, with no real felines, marsupials took over the spot in particular the Tasmanian Tiger (before it got hunted to extinction though a couple are still spotted every now and then). Youll find different types of mammals, reptiles, insects, etc occupying the same niche in different areas. There was a need for that niche to be filled, and it was (in some cases in a spectacular fashion, such as the Australian Death Adder, which looks like a Viper but is not. The whole of Australia only has elapid venomous snakes related to the Mambas and Cobras but the Death Adder, even though an elapid, looks and acts and moves and hunts like a viper).
The way this plays, is that there were many people who would have made a (better) Hitler! It is just that the time was not right for that type of idealogy/person/movement. If Adolf was born 10 years later, his niche would have been already taken by someone else. Same thing applies to Stalin, Lenin, Mao, Idi Amin, et al. They were simply one species filling a niche take the Jaguar (Hitler) out of South America (the World), and the Cougar (a far WEAKER species in our case, a weaker Hitler-analogue) would have proliferated far farther south (i.e. the rule of the new Hitler-analogue would have lasted far longer albeit in a weaker form, where Nazism rather than trying to be the dominant system would have become a competing system much like communism was ). Or maybe the American Lion (a far STRONGER species in our case, a stronger Hitler-analogue) may have still existed, and the entire North and South American continent would still have a feline predator bigger and more powerful than the Jaguar (e.g. imagine if Hitler never had syphilis, or if he was not STUPID enough to have attacked Russia, or if he was SMART enough to have waited 5 more years for the already superior German technology to have increased numbers etc etc etc .the Third Reich would probably still be on today).
If we went back in time and killed Michael Jordan, some other basketball player would have risen up and filled his niche. That TIME was looking for a player to idolize. Same thing with Shaq (who is not necessarily a good player), or Kobe (who is not necessarily the best player). Or with music ..take out Michael Jackson back then, and probably Prince would have become the next MJ. Or Cindy Lauper with Madonna. Or a whole host of Britney-types if Spears hadnt rose to the top of the lip-synching brigade!
Take out Hitler, and someone weaker (but far longer lasting) or stronger (with the Third Reich ruling the world) would be in place. He may not even be German maybe it would have been a Soviet super-state. Maybe the US would have ended up being the evil empire (a question I always ask those who believe in Bible prophecy, which I do just not in the way some do where they even know the countries involved, is where is the US in the final days? It is not mentioned the only great power mentioned is the entity the Whore sits on, called Babylon. So, unless the US is Babylon, it is not there. Once upon a time I would never have believed the US could be Babylon, but look at where it is heading. Anyways, let me stop what could be a thread hijack).
The second problem is that of unintended consequences. Like another FReeper said, take out WW2 and a whole HOST of Americans would never have been born. As he said, that war alone really did a lot to mix up the demographics and movements of Americans. Take it out, and even FR would not exist, and the whole history would have changed (ranging from JFK not being a war hero, and more importantly, his older brother surviving the war since he didnt get on that rather-crazy-but-heroic-and-ultimately-fatal mission of flying a bomber laden with explosives to crash it by parachuting out and using radio control that was the brother Joe Kennedy had groomed to be president; to Nixon, to Carter, and thus no Reagan and who knows). There is no way knowing that it couldnt have been far far worse. I always like to use the example of JFK (a man who I know is no conservative, but who is ironically far more conservative than most GOP leaders who call themselves conservative hed be to the right of the GOP were he alive today) and how he handled Cuba. Were there mistakes? Yes, many! However, had someone slightly weaker than him been in power, or slightly stronger, and wed either have had the Soviets setting full military camp in Cuba, or have faced thermonuclear war. Thus, I am happy with him being there at that time, because even though someone else could have been much better (and Cuba would still have been pro-US), there is a chance someone else would either have had the Soviets bristling closer than Taiwan is to China, or else sparked off WW3 by wafting 2 steps rather than 3 (or 1).
Or to expound on another example a FReeper brought up when he countered the post by another FReeper about Lincoln being snuffed out. No Lincoln would have meant slavery continuing longer than it did (yes, abolition was not Lincolns main goal, but it happened nonetheless), and the US economy would have continued being mostly agrarian, and the US would have remained behind Argentina (until the turn of the 20th Century, Argentina was more developed than the US) for much longer. Just like no Carter would have meant no Reagan, which would have possibly led to the USSR surviving maybe a decade longer; sometimes taking one un-appreciated element out can cause a cascading of bad things.
At the end of the day, the one person I would remove from existence would be the person who invented a way of removing people from existence in the past.
Refer to post 184 this thread.