Typical mind fallacy is "that person behaved that way for the same reasons I would behave that way, and they would like what I would like, and dislike what I dislike".

Even if you think you are special and different, you might still implicitly assume that everyone knows that crinkling that noisy bag of chips is annoying simply because it's annoying to you and therefore flare up in irritation at the one guy in the library doing so. You say "how inconsiderate", but they don't even notice when other people crinkle chips, so they think you just appeared out of nowhere and started being unreasonable and mean on purpose.

"Special snowflake" attitudes don't run counter this, it's an entirely separate thing, operating on a "higher" level. Your ego might think you're a special snowflake, but your id doesn't take that into account when you instantly react.