I'm not going to pretend that it's not true (after all, the author is a geek and wants to share that with other people -- there are plenty of comics for "non-geeks"), but it's definitely not true of _every comic_.
> The emotional response they evoke in the viewer is based on, "I know something that other people don't"
Personally, the xkcd comics I find funny are the ones I relate to (the same with any joke). In particular, this one on Machine Learning[2] was especially funny to me because someone in my research group recently started looking at neural nets to analyse stellar spectra and we had a similar conversation with a similar conclusion.
Just because very few people might relate to a particular comic doesn't mean that they relate to that comic because they like feeling superior (they might, but that's not what the comic is trying to do).
[1]: https://xkcd.com/1845/ [2]: https://xkcd.com/1838/
lol good one
Wait, are you a chicken? Is the classic galline joke not funny to you because you can't relate to a bird?
When you talk about finding that xkcd funny because you could relate its situation to a personal experience, I feel that was evoked from the feeling of nostalgia/coincidence; that certainly can be funny, but it's definitely not a joke.
Take the "people under the orange sun/red sun" joke from My Three Suns[0] (Futurama S01E07, 1999): it's not funny just because it's a callback to the same joke in Homer and Apu[1] (The Simpsons S05E13, 1994); or because it's satirizing the derivative "white people/black people" comedy routines (e.g. Eddie Griffin[2]) inspired by the set from Richard Pryor: Live in Concert[3] (1979).
It's funny because the comedian walks in a funny way, and talks in a silly voice. Very few people I know would walk & talk like this, yet (even without being able to relate to it) I can enjoy its humour. The multi-layered reference make it a deep joke, and the timing/acting/context make it a good joke.
My issue with xkcd is that it only uses the reference part, seeing that many great jokes include callbacks to other jokes, but missing the "being funny" basic requirement of a joke.
[0]: https://youtu.be/EZe7z73jKj8 [1]: https://youtu.be/L104LViQeIw [2]: https://youtu.be/o_RZusRfuw4 [3]: https://youtu.be/RL8Rru-lFmg