I've been called "Polack" for as long as I can remember. The bottom line is that it's not an insult unless the person means it to be. "Polak" is Polish for "Polish person."
See
http://en.wikipedia.org/wiki/Polack
On a different note: Saw the Qui Nhon in your post. Last time there was in November 2001 as part of a vet's tour.