It's really not rocket science. If animals are not mere things; if they have moral value, we cannot justify eating, wearing, or using them particularly when we have no better reason than palate pleasure or fashion. If you are eating, wearing, or using animals, then your actions say that you regard them as mere things, despite what your words say.

The distinction between meat and other animal products is total nonsense. Vegetarianism is a morally incoherent position. If you regard animals as members of the moral community, you really don’t have a choice but to go vegan.

We cannot talk simultaneously about animal rights and the 'humane' slaughter of animals.

Being vegan is not a matter of "lifestyle." It is a matter of fundamental moral obligation. Is being vegan a matter of "choice"? Only insofar as we are able to choose to ignore our moral obligations not to exploit the vulnerable.

We do not need to eat animals, wear animals, or use animals for entertainment purposes, and our only defense of these uses is our pleasure, amusement, and convenience.

Ethical veganism results in a profound revolution within the individual; a complete rejection of the paradigm of oppression and violence that she has been taught from childhood to accept as the natural order. It changes her life and the lives of those with whom she shares this vision of nonviolence. Ethical veganism is anything but passive; on the contrary, it is the active refusal to cooperate with injustice

...eating animals involves an intentional decision to participate in the suffering and death of nonhumans where there is no plausible moral justification.