I am vegan to try to do as little harm as I can. But really, there is no way to avoid causing harm in this world. We are prevented from being harmless by the structure of existence. We are forced into conflict with other people and our basic needs, and animals, and we are forced to harm others by the nature of the world, but I still try to harm as little as I can.

I am vegan because I hate life.

EDIT: I just realized, I didn’t answer the question. Need, for what? For their health? For the suffering of animals? I am not sure vegan is the optimal diet for health. But I don’t care, I am vegan for other reasons. If people hate the brutality of consuming animals then yes they need to be vegan.

Everyone is not a unit that will ever work together, the vegan “cause” is hopeless.