How can I say this without being offensive?

The fact that something is the norm does not have to mean it is superior, however, in a case like heteroism, the fact that heterouality is the norm leads people to believe that it is therefore superior. This idea of superiority by majority is present in lots of groups, for example, the Nazi or KKK concept of a 'master race' which is better than any other race simply because it is the most populous in that area.