Under the presidency of John F. Kennedy, the United States maintained its longstanding tradition of supporting unsavory regimes whose continued existence was deemed vital to American interests. Some of these regimes acted as bulwarks against the spread of Communism; others were willing to allow the United States to exploit its raw materials, such as oil. The regime of the Shah performed both of these valuable functions.
In a region in which Soviet influence was spreading and where there were large reserves of oil, the United States needed a dependable ally. Kennedy believed that he had found one in the shape of the Shah of Iran. During the Kennedy administration, a strategic alliance was formed between the United States and Iran, and it was hoped that this would stabilize Iran from within, thus making it less vulnerable to Soviet influence.
Although the alliance was generally successful, there were problems. For one thing, the Shah didn't make the kind of political and economic changes that Kennedy wanted to see happen. In particular, the Shah made no serious efforts to implement democratic reforms. Under the Shah, Iran remained an authoritarian state in which human rights abuses were the norm.
And yet, the United States continued to back the Shah for the reasons we've just examined. Some critics argue that this made Kennedy a hypocrite, preaching the virtues of democracy while at the same time offering economic, diplomatic, and political support to a despot. Some go even further, claiming that Kennedy's support of the Shah's regime made him complicit in the systemic abuse of human rights.
A more balanced assessment, however, would take a look at the bigger picture. Had Kennedy not supported the Shah, it's highly likely that his regime would have been replaced by one even more cruel and authoritarian. In fact, that's exactly what did happen in 1979, when the Shah was overthrown in the Islamic Revolution.
One should also note that Kennedy himself was highly critical of the Shah's record on human rights as well as his contempt for democracy. Pressure was put on the Shah to change tack, but at the same time, the Kennedy Administration still needed a strong, stable ally in the Middle East that would reduce Soviet influence in this most strategically important of regions.
And so Kennedy continued to support the Shah, not because he approved of everything he did, but because it was strategically imperative for him to do so.