`````

Shock, horror, sad. Probabaly the same way anyone with an ounce of empathey responds.

Though supposed it depends on which part of WWII you mean. The entire thing? Just the battles? The Holocaust? The social and economic effects?

Granted it all get generally same reactions just varying degrees.

Though from what we've seen or had hinted at MLP has some rather dark and messed up part to it as well.