World peace would be better served if we opposed any countries which tried to extend their influence beyond their borders and/or beyond the wishes of other countries.
Saudi is an ally because of convenience. They sort of help protect Israel. They fight back Iran. And they give us access to the Golf. They are also very friendly to our defense vendors, buying all sorts of weapons at good prices.
You could argue that these reasons are not good enough. You could argue that they teach forms of Islam that hates America. You could argue that they hate Israel too. And I would not disagree. But our state department chooses to take sides in the Iran, Saudi feud. They do this to keep Russia on one side and us on the other. They do this to keep Israel around as well as Jordan and Egypt. It may be a pact with the devil but its been around since world war two.