AmericanCulturalAssumption. Very much in common usage in the Good Ol' US of A.
The LoneRanger & Tonto are riding down into a box canyon. At the far end, the LoneRanger notices an army of Comanche Indians, in full war-paint, frowning down from the cliff walls at him.
Turning to his left he notices a great number of very mad looking Arapaho Indians staring down.
On his right he observes a host of Cherokee Indians peering at him over the rim of the canyon.
Looking behind, he sees every Apache brave in the world slowly creeping into the canyon, blocking the exit.
The LoneRanger turns to Tonto and says, "We're in a heap of trouble, Tonto!"
Tonto's nervous reply, "Uhh...who do you mean we, pale-face?"
Those of you under hyper workplace harassment clauses can substitute "Kemo Sabe" in the punchline... One works because Tonto's pointing out there's only one non-indian in the situation, and the other works because "Kemo Sabe" is alleged to mean "faithful friend".
Another punchline is, "What's this 'we' shit, white man?". (I, too, wish those darn European-Americans would quit being so sensitive about being called "white".)
I'm not sure why substituting Kemo Sabe would make someone less offended by this joke. It's inherently racial as it is, and if you get offended by that, then saying "Kemo Sabe" instead of "pale-face", "whitey", "jarhead", or whatever isn't going to make any difference.
The moral of the story: Use this (carefully) when you hear someone say "we" and you need to count yourself out.