"The things I disagree with are the parts where he implies that many non-Western civilizations are not ready or less able to adapt to democracy."
I don't think that opinion is all that controversial. Nor do I think it implies the superiority of Western Culture, in itself. In the West we take our liberal attitudes for granted, as if it were the most natural way of thinking. Take for example the emphasis on the individual in the west. From our perspective this is view as morally righteous, but in other cultures the concept is viewed as corrupting as it overrides older loyalties such as to the family, the tribe, religion (or other larger social units). But individualism is a core part of democracy, as we in the west know it. It is almost a cultural prerequisite for democracy. Furthermore we assume that democracy is desirable. And for us it is. Our democratic systems of governments provide political cohesion and stability, but this is not necessarily true for other cultures/societies. Democracy could in some circumstances be destabilizing, and not of great benefit.\
"In his essay about Hispanic immigration in the US he says that they compromise America's values and don't assimilate into the culture."
George Friedman shares similar views. In his book "The Next 100 Years" he postulates that the border region of Mexico and the United States could conceivably become part of Mexico again one day. That some of the immigrants who live in that area, are more likely to maintain older loyalties, especially as Mexican friends and family are so close by, and thus still see themselves as Mexican. Wheres those Latin Americans who live further away from the border are more likely to assimilate and see themselves as American.
This is not to denigrate Mexicans but is rather a product of human nature. Once the situation was the other way around. Texas and California we part of Mexico and it was the Americans who were the immigrants, but immigrants who were not interested in assimilating with Mexico.
Is this really true of Mexico and the United States, speaking for myself, I honestly don't know if it is true, but I can appreciate the reasoning.