I occasionally review my posts to see if I said something I want to retract. I don't edit out what I said, but have commented on myself a few times. Recently, at the Lake Superior Free Thinkers regular meeting, we had a philosopher, Shane Coultron, speak who corrected me on something I've mentioned now and then. That is, I have said I can't find a similar statement about the Christian idea of "that which you do to me (Jesus), you do to the least of these (i.e. the poor or sick)."
Turns out that is addressed by modern philosophies, it's just not as easy to find in a short concise phrase like it is in the New Testament. Shane gave me several examples:
Utilitarianism - If you are simply adding up happiness and basing choices on increasing it, you would do well to focus on down trodden, poor, sick people. Their happiness rating is lower. This is born out with sociological data, although there are those communities of people with limited means that are quite happy. Utilitarianism does not make broad generalizations about what it takes to be happy. The important application of it here is that if you focus on those who have the most needs, you will make the most difference in increasing their happiness and likewise increase overall happiness for all. This includes the assumption that even if you are well off, it makes you sad that others aren't. Again, plenty of exceptions to that assumption, but they don't matter to the overall score.
But Utilitarianism has other problems, and I don't like defending it too strongly.
I prefer the more subtle assumptions and laws discussed in what is sometimes called Social Contract Theory. The idea that we came out of the jungle and made agreements to act in ways that are mutually beneficial. In this system, ignoring the needs of any group has a cost. If there is not good reason to restrict someone's rights or to not reward them for their contribution, they can reasonably consider the social contract to be broken. As society has advanced, we have created better peaceful means of addressing these grievances, but many remain.
History shows us how this plays out. Marx's analysis of the cycle of cultures working together to increase their wealth, then that wealth becoming concentrated, then revolution, has strong historical data to back it up. We see it happening again now, but we also see more negotiating under way. Hopefully this time around we will acknowledge "the least of these" and find a way to re-establish the contract.
I'll just mention that Shane said Kant's de-ontological ethics also addressed this issue, but I don't find Kant particularly interesting so I leave it up to you to look into that.