I can understand why someone would ask who the good guys were in WW1.

It's a question that shows a childlike understanding of war in general, but that's how war is often sold. A team sport with body bags.

That said, WW1 is hard to pick a "good" side. It was a mess of a war, but no side was particularly vile when compared to the others...

But for a US president, there's only one valid answer.

A US president can admit that Vietnam was not a shining moment is US history, but the world wars? No.