I'd say it also attaches far too much importance to genetics. Had Hitler's mother died at birth and Alois married someone less enabling of Hitler's childhood predispositions, things would have been equally different.Of course, there's nothing to say that someone else might not have had similar ideas to Hitler and taken his place. The details are different of course, but the thrust of history would be the same. Then again, obviously, there's nothing to say it'll remain the same. Still, factors that shape so-called great men might still exist to shape other men into greatness.
Or maybe people just aren't as important to history as we would like to think. If Hitler did not exist, maybe the time and circumstances were just right for the Nazis to arise. Somebody else would have been Hitler instead.
Like I mentioned before, if Edison had not lived maybe the time was just right for the light bulb?
The conditions that allowed Hitler to thrive would've been present regardless of whether he was or not, because WW1 still would've happened. You'd still have alot of bitter, pissed off Germans and someone would've capitalized on that sooner or later.
Take out Edison, and we'd probably be looking at Tesla instead. The face of technology would be different, and we may have some things we don't have and vice versa.
The Wright Brothers weren't the only people trying to build aircraft...there were several others also working on powered flight.
If Rush Limbaugh did not exist, you'd still see the rise of conservative media because conservatives were getting fed up and angry around that time. It may have happened a little later, the names would be different, but the conditions were there for someone to thrive.
As for altering the past creating a parallel universe....until someone can explain how preventing two people from fucking (or any other Earth based change) generates enough energy to create a universe with several thousand galaxies, each containing billions of stars, I'll pass on it.
For time travel logic, I generally hold to Anderson's "Time Patrol" series.
One of the most creative time travel series I've read was "Time Breakers"
http://en.wikipedia.org/wiki/Time_Breakers