In very simple terms, animal liberation means that humans will stop exploiting and slaughtering 85 billion land animals every year, trillions of fish and marine animals will no longer be dragged out of the dying oceans and the rest of the free-living animals won't be facing the danger of extinction because of human actions.
We would also need only about a quarter of the land we currently use for growing crops to feed everyone, leaving the rest for rewilding and global greenhouse gas emissions would be reduced by about 15%.
If that's not worth fighting for with everything we've got then nothing is.