Are all cultures equal or are some cultures superior to others? The question is difficult to answer without clarifying what is meant by "equal." Usually what's referred to are the values of a particular society, and the assertion that all cultures are equal is equivalent to saying that all values are equal.
This would seem to be a very difficult claim to defend, but it's popular today among those who call themselves "multiculturalists."
Multiculturalists are generally ethical relativists who believe that moral right and wrong, good and bad values, are determined by the time and the culture in which people live and that no culture's views on these matters is superior or "better" than any other culture's views. They're just different.
It follows, then, that a culture that produces hospitals, charitable organizations, modern science and technology, women's rights, Bach and the Chartres Cathedral is no "better" or "worse" than a hunter-gatherer culture that produces nothing at all or a culture that condones and practices slavery, wife-beating, female genital mutilation, honor killing and infant sacrifice.
This is certainly counterintuitive, but it follows from the postmodern denial that there exists any objective moral standard. If right and wrong are simply arbitrary cultural conventions, like a preference in food or dress, then how can one group claim their conventions to be superior to another group's?
Dinesh D'Souza argues against the multicultural view in this short video from Prager University. See what you think: