> if they would suddenly adopt human rights, democracy and other western policies, they would most likely not stay in power for long
I think you may be right (I haven't enough information about Saudi Arabians or their views to tell) but I really want to believe that the real-life politics is much more rational than in a game of Civilization.
Well, that's been the case with Arab spring, Syria and Lybia: when US sees (often, mistakenly) that faction with more westernized values can take over, US supports it.
However, it is completely rational: "spreading democracy" is valid not only from idealism, but from the notion that it's much easier to deal with governments and societies that share your values. Of course, US have not always followed this motivation throughout history, but in case of islamic arab countries in the last years, US has pretty solod record in that regard.
I think you may be right (I haven't enough information about Saudi Arabians or their views to tell) but I really want to believe that the real-life politics is much more rational than in a game of Civilization.