I'm a little confused as to why people think dumping cables from American embassies would show the US in a negative light or contain some sort of revelation tha

I'm a little confused as to why people think dumping cables from American embassies would show the US in a negative light or contain some sort of revelation that the US is engaged in anything illegal. These are cables from the American point of view of the rest of the world. If anything, it is going to show foreign leaders/countries far more negatively than the Americans.