You are absolutely correct about the devastating effects of deforestation caused by avocado farming.

The simple truth is that the agricultural infrastructure necessary to currently support the human population is killing animals in crueler ways than the meat industry. And with only ~4.9% of the planet eating a vegetarian diet, the idea that veganism will somehow end animal suffering by changing the human race's diet to purely plant-based is entirely ignoring the destruction of the current method and infrastructure that is necessary to feed the 95.1% omnivorous human population now, and is thus the most obnoxiously pretentious of all the anti-intellectual movements that currently plague the Western world.

Tl;dr The only way to save animals is essentially annihilating the human species, as our methods of feeding ourselves will inevitably end animal lives on a massive scale. Period.