Why do the u.s denounce certain leaders and yet support dictators in certain countires?

the third reich (u.s ) have called former presidents like saddam hussian and slobavan milisovich as dictators and yet they have supported and still support evil dictators in a lot of countires. A good example would be the former general pinochet of peru, who was responsible for killing over a hundred thousands of it's people, he was even allowed to have a heart operation in the u.k in the 90's. the marcuses of the philipines who oppressed and killied thousands of its people, same as the former shah of iran who did the same thing and there are many present day dictators who are in power which are still supported by the third reich(u.s). It's obvious to the world that if a country has certain natural resources such as oil and minerals which the nazi's need it will support or put in power dictators of these countires so as it benifits the third reich (u.s) and not the people the dictators oppress.what do people think?