But what constituted moral killing of animals in the past is not the same as what constitutes the moral use of animals today is not the same as what constitutes the moral killing of animals in the future is not what constitutes the moral killing of animals on the first day of the world.
That is a point of disagreement between you and I.
I don’t subscribe to moral relativism, and what was moral yesterday is different than what is moral today.
The nature of animals have not changed, and what would have been cruel and painful for animals yesterday, or at the beginning of the world, would be no more or less painful for the animal, and no more or less cruel on our behalf if it happens today. Our standards of what we consider to be moral changes with greater understanding. The actual morality of an act is timeless.
The morality of a practice depends on our knowledge of the overall impact of that practice balanced with its necessity in the good of human society.
There is a rational argument to be made along those lines.Admonishing people that the Church has changed teaching with the circumstances is not an argument that follows rationality, but is a dogmatic argument.
The dogma of the Church on killing animals or on capital punishment has not changed. The opinions of many church leaders have changed over the years, but that is not the same as a change in teaching.
Take for example the fact that years ago before the pedophilia scandal came to light, Churchmen followed the expert opinion of the psychiatric and psychological communities that pedophilia was a malleable condition, and that forgiveness, acceptance, and unconditional love of the sinner was the solution.
This did turn out well for the Church. Thankfully, it never became an explicit dogmatic teaching of the Church either.
The same is also true of capital punishment. It is up to the bishops involved to make the argument for the case against capital punishment humbly, with full recognition that their opinions are not God’s own truth. It is up to us to weigh the evidence against our own conscience and the arguments of others, rather than to accept everything out of a pope’s or a bishop’s mouth as dogmatic truth and infallible Catholic Doctrine.
Those elements are a constantly changing variable throughout the entire course of human history. There is no historical period that can claim the divine default in addressing use of the death penalty. In every age, its use or abolition depend on the needs of human society in creating justice within the community of men. It’s use or abolition is always a matter of prudential judgement that revolves around the concerns of the common good.
Likewise, ever case in every age is different. There are some cases where capital punishment is clearly the worse choice, today, yesterday and tomorrow.
Likewise, there are individual cases where it will be much, much harder to make those arguments.
At any rate, it is the arguments that must be made for these cases. Bishops play a crucial role here, but one is not required that what any bishop teaches on capital punishment rise to the same level of de fide belief as the core of the faith, such as the Resurrection, for instance.