I completely disagree. Scan this thread for my thought experiment about the pill that wipes your memory back to the state it was 30 days ago. I haven't overlooked the point you are making.
> If there is no afterlife, then eventually there will be nobody left in the world,
Whether or not there is an afterlife, it is inevitable that the earth will become uninhabitable. It seems far more likely that humans will die off before that becomes a problem.
> in which case nothing that anyone had ever done or said would have really mattered
Like the old joke about fish not being aware of water, I think people who have spent their entire lives in a Christian mindset forget that the novel thing Jesus was offering was an afterlife. Many cultures and religions believe a person simply stops existing when they die (including Judaism), yet the people without a belief in the afterlife still seem to care if they are happy or miserable.
Let me try another tack along the lines of the thought experiment I stated elsewhere in the thread. Christians believe in a personal soul that outlives the body it is tied to. I'm sure some Christians might think that some animals have souls as well, but I'll go out on a limb and say most don't believe, say, a beetle, has a soul. If you came across me torturing beetles with salt, or fire, or pulling their legs off, you'd rightfully think I'm a horrible person. Why would it matter? After all, the beetle has no soul and will be dead in a few months anyway. It is because even though the pain is temporary, it is very real while the beetle lives through it.
Jews did believe in an afterlife - read about Sheol, for example. Not sure where you got that idea from. They thought that death was permanent, but that is a very different thing from thinking there's no afterlife. There are also two Old Testament figures - Enoch and Elijah - who were brought up into heaven. What Jesus taught that was new in this regard is a bodily resurrection.
Also, all animals have souls according to Catholicism, and so do plants. The distinct thing about humans is that we have rational souls. But the soul is the form of any living thing.
Torturing an animal is wrong because it does harm to God's creation for no legitimate purpose. A theist doesn't have any problem explaining this - it's the atheist/materialist who does.
To be fair, several (at the time) large religious groups believed in a spiritual afterlife. What disgusted many Greeks & Romans was the concept that a _bodily_ afterlife was the ultimate destiny of a human.
> If there is no afterlife, then eventually there will be nobody left in the world,
Whether or not there is an afterlife, it is inevitable that the earth will become uninhabitable. It seems far more likely that humans will die off before that becomes a problem.
> in which case nothing that anyone had ever done or said would have really mattered
Like the old joke about fish not being aware of water, I think people who have spent their entire lives in a Christian mindset forget that the novel thing Jesus was offering was an afterlife. Many cultures and religions believe a person simply stops existing when they die (including Judaism), yet the people without a belief in the afterlife still seem to care if they are happy or miserable.
Let me try another tack along the lines of the thought experiment I stated elsewhere in the thread. Christians believe in a personal soul that outlives the body it is tied to. I'm sure some Christians might think that some animals have souls as well, but I'll go out on a limb and say most don't believe, say, a beetle, has a soul. If you came across me torturing beetles with salt, or fire, or pulling their legs off, you'd rightfully think I'm a horrible person. Why would it matter? After all, the beetle has no soul and will be dead in a few months anyway. It is because even though the pain is temporary, it is very real while the beetle lives through it.