Situations like this is why there needs to be diversity training in schools. Diversity training does not mean you HAVE TO LOVE other races and ethnicities, just understand what people have gone through to make it in this country. For example, when many uneducated Irish people came over because of the potato famine they could only get low-wage jobs and lived in slums. Now, if I decided to have a party and have people dress up as poor Irishmen, talking with a bad Irish accent and acting like they are begging for potatoes, then some might consider that to be racist. There are many sterotypes we can all abuse.
What I consider sad when I hear about situations like this is that it seems like the only way White frat boys can have a good time is to make fun of other people, and that is just pathetic.