"Racism" can be used to describe discrimination on cultural and/or ethnic grounds. So.. its use in this case is appropriate. It doesn't require that the subject is a distinct "race"....

As an aside: "race" probably does not exist as an entity aside from culture and ethnicity anwyays. The notion that "races" exist might in fact, be , a "racist" attitude...
The first few paragraphs of the wikipedia page on "racsim" make for some interesting reading.

While were at it look up fascism and think about who was really getting a rough time with discrimination.