It's offensive because it's an over generalization that being a certain race means you like a particular kind of food. To assume a Japanese person likes sushi or that an Italian likes pasta and meatballs is very similar. Certainly its pretty low on the offensive scale but it's such a lame joke anyway. Tiger Woods is what, a quarter black, so it doesn't even make much sense. Oh you're grandma was Native American, I think your new nickname should be Tonto. Just dumb.