Shame you didnt order a Japanese made tazer, that might have fixed his tone up a bit. Nothing worse than rude customer service staff (and I work in client facing myself).
Perhaps his derision comes from his own knowlege of Japan, and what he's most seen from there
I'd consider putting in a complaint about him to be honest, if you work for somewhere like the mail, it's your job to deliver the post, not judge something by where its come from. Theres a LOT of things that could come from Japan, electronics, whatever, (hell it could even be from family) however judgmental fools like that get on my nerves.
Again, thats just my personal opinion, but if you honestly feel he was taking the mick, you ought to put in a complaint. If he acts like that to other people using the mail, he needs taken down a peg or two by his boss.