I'm not defending his ideology, but its important to understand the rational reasons behind his decisions if we want to prevent another global catastrophe. Even without Hitler its still likely Germany would have instigated fighting at some point.
Another way of looking at it is that the fighting resulted because France and the allies didn't crack down on Germany when they failed to meet the terms of their surrender.
Personally, I feel that your view (and the conventional view) is more correct, but it's interesting to think about the converse. I mean, we've still got troops in Germany today, right? What if that's the key? It wasn't about economically rebuilding them, but what if, instead the war didn't flare up again simply because the occupation never ended?
Hitler did not valued life and got used to violence in WWI. That has nothing to do with intelligence either. Both stupid and smart people can grow to not value life and be ruthless and confident and power hungry and taking too much risk.