There's also the ethnocentrism aspect of it too.
These people are convinced that they are inherently better than others and that's the only explanation they need for their hatred.
And incredibly, it seems to be really heavily weighted on white (sometimes English specific) supremacy, no matter which country you are in. The video in the article above made the point about how the Polish people didn't discriminate against the English people in their country, which really goes to show how one sided these things can be some times...
Not saying other forms of discrimination doesn't exist, it just never seems to go to the same degree.
Like the KKK in the United States and racial hate crimes here, race hate against "white" people is unheard of >.<
(Let me know if my discussion may be getting too controversial or if you are uncomfortable at any point :P)