Seppo's, Pommies, Kiwi's, Krauts, Tommies, Yanks, Cannucks, Frogs, Yvan's, Hadji's, Wetback, Redneck, Cheesehead, etc
I think we are all pretty guilty of using our own versions of slang in and out of official publications. A bit weird for a Yank to take offense to being replied to in kind. If we are all denoted by slang names then no-one then we are either all offended or no-one is.
Wouter