If the US cares about human rights so much?

why didn't america do anything when shah killed thousands of people in one day? then again next month he would kill another thousand? not only the US didn't do anything but they supported him. if the us cares about human rights why it didn't do anything when iraq used chemical weapons against iranian CIVILIAN? killing tens of thousand of people in the city of halabche? not only the us didn't do anything but the west sold weapons to saddam.