They would not seriously claim that English and Scots were a different race, but it's hard to find a better word than "racism", despite its obvious inadequacy, to describe the worst cases of these anti-English (and the other way around anti-Scottish) feelings. "Racism" is often used in a wider meaning than its literal one, for the simple reason that "ethnicitism" is not an existing word. And "discrimination based on ethnicity" is too long.