That’s a good point; as we were the “anti-Cuba”, he probably assumed we didn’t have liars in the media...
The idea that they would lie to make the US look worse does not make sense to him. Shouldn't they love their country and want their side to win?
It would sort of be like finding out that Ernie Pyle was sending back false reports of Japanese victories and US "war crimes". It is just unthinkable.