what does it mean?

Please comment on this post before you read anyone else's comments.

This weekend, I saw a bumper sticker that said,
Straight, White, English-Speaking
Proud American
For a moment, I was offended ... then I started thinking of several different possible intentions, meanings, and contexts for this slogan. After a bit of confusion, I settled on curiosity. What does it mean? What did the people who sold it intend for it to convey, and what did the person who put it on their car intend to say by it? I can think of several different possibilities or nuances, and maybe there are more.

So tell me, what do you read in this bumper sticker slogan? And if, like me, you see several possibilities, which one came first, before you thought about it?