When you're homeschooled, I find that people place stereotypes on you as well. If I meet someone who asks me where I go to school, they assume one of two things.
1. That I'm a pasty kid who never has social interaction and believes that all democrats should be taken out onto the street and shot because of failure to worship the shrine of president Reagan. (^^)
2. That I dropped out of school and the whole "homeschooling" thing is just a coverup.
You would be surprised to learn how many people still hold this viewpoint.
So, I can understand why an Asian person would take offense to that book. When people make presuppositions of you, they tend to stick with them. Not get to know you as an individual. I know some of my friends who are Chinese get really annoyed when this happens. But I don't know if I would say the authors meant any harm by it. *shrugs*