To be fair, if I made a hugely obvious social mistake in public, if someone shouted "mistaaaaaake!" I'd probably be annoyed, as JD is in the gif.

If someone pronounced it as the caption describes, I'd probably still be annoyed but refocus on how someone could make that kind of mistakey.

If someone pronounced it as "mis-stake-eh" it probably wouldn't help in the situation but might actually cheer me up in the face of what would otherwise have been despair.

Mistakey sounds like something that's technically a mistake but only a little bit (will incorporate this into my vocabulary).