Do you think past mistakes, Ike's or whoever's, absolves Carter of his?
Carter was really in a no-win situation on this particular issue. Do the Clinton administrations blunders in the 1990s absolve the Bush administration of its responsibilities for 9/11? I think they do, for the most part.
I would like to correct you on something: Iran was never actually "colonized" by the British. It was only occupied for a while during and just after WWII by British and Russian soldiers.
Modernization of Iran began during Reza Shah (The late Shah's father) and due to his initiatives.