The so-called 'white culture' IS the universal culture. It has the best many cultures had to offer: Greek, Judaic, Arab, Chinese, Japanese, Indian, Anglo-Saxon, French, German, Russian and whatever was worth taking from other minor ones. The fact that nothing or not enough of whatever some inferior cultures might have produced it usually because their contribution was just that - inferior.
The multicultural/diversity drive is that of forcing the civilized world to accept the products of inferior cultures as if they were as valuable as the those who found themselves a place within the 'universal' one. The only way 'barbarians' can participate is by first asimilating. There is also the option of them (the barbarians) trying to destroy that which is superior so that only the inferior products are left (see the Talibans bombarding the Buddha statues).
Of course, this tradition has been under attack for well over a hundred years. The latest assault has taken the form of deconstructing the tradition to show that it is, in fact, and oppressive system of control.
The problem, so far as political philosophy is concerned, is to reconcile the natural rights teaching with the demands of modern natural science. Some sort of teleological basis for normative values is what is lacking.