Bad interview questions are actually quite useful, as an indicator that the company is not somewhere you ought to work.
Enough people who can't code apply for software development jobs that asking a simple thing like "Write a sort function" is a good filter. Why waste 10 minutes on a better question when he can eliminate 50% of the applicants in 2? The interviewer doesn't think you're dumb and he's not trying to snub you - it's just how interview questions work.
If you're such an amazing developer you shouldn't have a hard time writing a sort function. Spend the 30 seconds to write the sort routine and get over it.
True story, i know a guy who was denied a job at FB after an interview, a few months later they ended up giving him a few hundred thousand after they acquired the small company he ended up working for. He now works for FB.
Interviews are poor indicators of performance.