"But since there's no "earth" at the north pole, the correct answer is obviously the south pole."
That isn't correct at all. First of all, you can't walk south from the South Pole, but that doesn't even matter because:
He says the surface of the Earth. He doesn't say what that surface is made of (i.e. Ice works), or even in what millennium you are walking in (see also Plate tectonics )
It's certainly some point near the South Pole, since the North Pole hasn't got any earth.
That would seem to be a problem, but is it as insurmountable as the fact that the South Pole doesn't have a South? (and anywhere near it would suggest many possible answers, none of which could be determined during an interview.) FTA:
You're standing on the surface of the Earth
He doesn't say what that surface is composed of, and I'm willing to bet that it is not that kind of trick question, since that would be a stupid way to asses someone's intellectual prowess to say the least.
"Really? You must not do much real-world programming then. "
If anyone had any doubt they need only look at that statement. No competent programmer is so lacking in logical facility that they would draw that conclusion. Period.
"Basically, your assumption smells like the shit hole you crapped it out of."
That smell is your breath. Later, moron.