This came up in discussing intervention in Iraq, where we have something to gain, versus Darfur, where the humanitarian need is if anything, greater, but we have no national interest.
It sounds very kindly, doesn't it? Marshalling the resources of the country to intervene in some country where people are being oppressed, making the bad guys go away? Doesn't that just seem better than only intervening when we have something to gain from the endeavor? It seems generous, noble.
It is in fact immoral and irresponsible. We should put our people at risk only when it is necessary.
The confused thinking comes from imagining the nation as an individual. The individual morality of putting oneself at risk with no promise or even hope of benefit is quite high. But that premise does not extend to sending other people into danger.
As an analogy, imagine that you are an 8th-grade teacher in a city. Farther downtown, there is a dangerous neighborhood, where gangs or ethnic groups engage in violence. You get the brilliant idea that going down there and trying to spread hope, pass out food, or trying to get group leaders to talk together would help. If you go yourself, risking your own neck, I would say that you have done a brave, kindly, and perhaps even helpful thing. But if you take your class down there, you should be fired and the parents allowed to put you in the stocks or something.
There might arise a situation under which the entire city is in such danger, and immediate danger, that bringing your class down to sandbag the levee would be moral. Even if they were in danger and you had to arm those who had firearm training, or shoot looters and muggers yourself to keep them away from your charges, you might be justified. But when you are responsible for people, you have no right to put them at risk unless it is necessary.
The tendency to confuse the concepts of "government" and "society" is more common on the left than on the right, though it is certainly not absolute. This is in turn a more natural development in people who are less likely to be married, and even less likely to have more than one child. Married people, especially women, tend to vote more conservatively. Even more so, married people with two or more children tend to vote conservatively. There are of course single paleoconservatives, and near-marxists with 7 children, but as a trend, married with two or more children equals a reliable dominance of rightward voters. I have a private opinion based merely on observation that having raised multiple children past the age of eight creates yet one more winnowing of liberals from the pool, and this persists until all children have been grown for a decade, at which point the conservative dominance begins to weaken.
Whether this is cause or effect is difficult to discern. People who are already conservative might tend to want more children, for instance. It is not necessarily marrying and having children that influences one in a conservative direction. But I think in this issue of necessity versus humanitarianism, having to be responsible for the lives of others gives one a deeper understanding of what a government should do. There are other roles in society in which one is responsible for the lives of others in ways great and small. The greater the responsibility, the more likely that role is occupied by conservative-leaning people. Applied scientists tend to be more conservative than theoretical.