In altruism you don't expect a reward but with a vegan lifestyle you get one anyway. You get your health. Not just physical but the mental health of a clear conscience.
I suddenly remember, I accused my parents of being 'hypocrites' when I was 11. Big word for one so young really! I wanted to know why, on the one hand, they said that beauty came from within and on the other they referred to me as the ugly duckling! Furthermore, they said that equality was important but there were certain friends that they didn't want me to have.
I have always felt that we should continue to examine ourselves through life and hold a clear intention to be part of the solution, rather than part of the problems as we become aware of them.
No one will ever persuade me that butchering 60 billion land animals and 90 billion marine animals every year is okay. Tell someone else that it is somehow in our Nature/Nurture patterns if you want to justify nibbling away.
I see the general diet as involving a massive denial of suffering and an unconscious participation in a brutal degradation of life - animal and human.