During the Cold War, the West supported people as bad as the Saudis are today. Nations dont have principles, they have interests.
They supported people as bad as the Saudi's, with the understanding they would become better as economic development occurred. Look around the globe, whether its the Phillipines, Panama, South Korea or Chile, it all came true. Compare and contrast with the middle east, whether its Mubarak for us, or Gadaffi for the Soviets, it just hasnt happened. Every tax dollar put into Saudi Arabia just seems to make them more decadent and intractable.
As for the second part of what you write there, that keeps being touted, but its ridiculous. Its the morally absent foreign policy cooked up by sociopaths like Kissinger. Yes, there are inherent advantages occasionally in behaving that way, but were it true the US would not have remained engaged in Europe for so long. There was no real economic reason why we gave the Irish Republic an 8 Billion pound float at the time of the financial crisis. Friendship is but one explanation for it.
Democratic nations all need each other right now. The ones that arent? Let them be the millstone of the unfree world. Because that is essentially what the Saudi's are becoming as their oil becomes less and less important.