I would encourage them never to forget that they were not always vegans. The self-righteousness of the recently converted hurts, it does not help, other animals.
The other animals humans eat, use in science, hunt, trap, and exploit in a variety of ways, have a life of their own that is of importance to them apart from their utility to us. They are not only in the world, they are aware of it. What happens to them matters to them. Each has a life that fares better or worse for the one whose life it is.
What could be the basis of our having more inherent value than animals? Their lack of reason, or autonomy, or intellect? Only if we are willing to make the same judgment in the case of humans who are similarly deficient.
It is not larger, cleaner cages that justice demands...but empty cages; not traditional animal agriculture but a complete end to all commerce in the flesh of dead animals; not more humane hunting and trapping, but the total eradication of these barbarous practices.
It is not an act of kindness to treat animals respectfully. It is an act of justice.
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