With the youth I'd say this generation is more affected by any other by the sheer noise of modern media. It's also one of the first where there was less emphasis on indoctrinating people towards the government's view on the cold war, the first to grow up with a government that lied to them about a significant non-cold war war (Iraq), and the first that actually has the means to cheaply find other views on things.
So maybe it's not so strange that young people think this way.
I mostly blame the Iraq war. Yes, the west has done a lot of bad things in the past. But in recent memory Iraq stands out as where we blew any pretense of moral superiority. (It does happen now and again, but the Cold War is a really good excuse for a LOT of bad things). People would have seen this and seen that whatever our governments say, you gotta take it with a grain of salt.