I have my facts. I'm looking for counter-arguments to my side, so I know what to expect, and have time to prepare against them.
Then, like every situation, "moral obligation" has it's limits and situations. It also depends on your culture and religion, and how deeply ingrained you are in this religion.
Although the teachings of many prophets (Jesus, Mohamed, Buddha, etc.) have passages that relate to the "moral obligation" to help the less fortunate (sick, injured, poor, etc.) many of the followers of those religions do not do so. This relates directly to the level at which the follower of that religion believes in the faith they proclaim to be associated with (various sects of Christianity, Judaism, various sects of Islam, Buddhism, Hinduism, etc.).
If you are asking on an individual basis (what we, the members of this board, believe and/or support) then my personal belief is that we have an ethical obligation with limits.
Humans are, by nature, social. We learned early on that if we formed communities we could not only divide work to prepare for seasons when food was scarce and protect ourselves from the elements, we could also defend ourselves from the elements of nature, predator animals, and predator human tribes. A community also provides for a larger gene pool. Communities are far more efficient than individuals or small family units.
In some primitive societies, it was customary for the elderly or members with an infirmity to voluntarily commit suicide by leaving the safety of the community, ridding the community (and their families) of the burden of caring for them when resources were so scarce. This was especially true of migratory and nomadic groups. (I would like to say that this was not in all cases.)
The purging of unhealthy members of a society is not limited to adults. There are many examples of infanticide. An example of infanticide can be found among indigenous people of the Amazon. If a child was born and did not look normal, the child was either taken to the jungle and left alone (to die of exposure, or to be eaten by wild animals) or a rock could also be placed on the infant's chest impairing it's ability to breath. Another example among the indigenous people of the Amazon is the high frequency of warring which occurred between tribes/communities. Women were captured to be taken as "wives" and their infants and small children had their heads bashed against the rocks to kill them. (It makes no sense to provide for the offspring of your enemy, and breast feeding impairs ovulation.)
In a society where the society is working hard for their survival, caring for the less fortunate makes far less sense.
In a more advanced society, this is not the case. Resources are not scarce. We efficiently farm and ranch to produce an abundance of food in Western society and other parts of the world.
There is a limit, however. Basic food and basic shelter are all that are required to meet the needs of any individual, "less fortunate" or otherwise. I live within my means, everyone else should do the same.
The most efficient way to provide support to the "less fortunate" is by means of pooling resources.
Homeless: shelters, "soup kitchens". Shelters have the power to pool sums of money together to purchase food and other items at a lower cost than an individual. I never give money to the beggar on the street, ever. If I'm willing to give him/her a dollar, I give it to the shelter where it will do more good.
Working poor: Habitat for Humanity. Many working poor remain in a vicious circle of bad credit and financial doom. Habitat for Humanity, with the help of volunteers, provides families with affordable housing to help break that cycle.
Nearly everyone can work. They can do something. Mow lawns, clean houses, bag groceries, etc. There are those who can not do anything at all and they SHOULD be cared for by their families with minimum help from society.
More later... gotta eat breakfast.