for G-d's sake...

conjure for me, if you will, the gustatory nirvana that is fresh guacamole. the buttery, hefty puree of avocado, the piquant citrus juice, the biting salt and cayenne pepper, and perhaps some crisp chunks of red onion or cilantro.

so what is missing from that Platonic ideal of guacamole?

oh, yes, the one ingredient so inessential, so misplaced, that you almost forgot people would include it.
Tomato.

It NEVER belongs in guacamole (if I ran the world, it wouldn't belong in anything, but I'm taking baby steps here).