> bringing Democracy does not make a population automatically Liberal

Nobody believes this to be the case. What is more often missed by policy makers is that overthrowing a government supported by the local population is unpopular and will cause blowback. The CIA-supported coup in Iran is a currently relevant example.

> Also, contrary to your theory, most of human history people were ruled by non-democratic governments that were deemed legitimate

That was when people believed in the divine right of kings, so those kings ruled with the consent of the governed. This is no longer the case. Nobody believes in the divine right of dictators.