Even Christopher Hitchens, who opposed the Vietnam War, writes today in Slate that there is no parallel "whatsoever" between Iraq and Vietnam. But even Hitchens fails to articulate clearly the obvious: North Vietnam was a disciplined, well-armed nation-state attacking South Vietnam. The U.S. never invaded North Vietnam and never sought to overthrow the North Vietnamese regime. The situation was thus stacked against the U.S. from the beginning. The U.S. did not seek to destroy the real enemy in Vietnam: an attacking nation-state.
Someone said somewhere that people always tend to keep fighting old wars. That's what so many so-called experts and pundits still do. They keep re-fighting the Vietnam War even though we are in a radically different time and place. This danger of overrelying on one particular historical episode has a parallel in moral theology. When it comes to matters of Christian ethics, I like to follow this analytical rule: "We must never generalize the particular; but we must, sooner or later, particularize the general."
By that rule of thumb, I mean that the moral solution to a particular situation can never be automatically generalized without engaging in hard analysis. For example, we all pretty much agree that Martin Luther King and Gandhi were right in pursuing non-violent strategies in their struggles. But, in both cases, they were functioning in a democratic, "rule of law" Anglo-Saxon milieu where public opinion could be swayed by a free press. But their success does not mean that such non-violent strategies can be blithely generalized to other settings. Hence, we must never simply generalize the particular.
On the other hand, sooner or later, we must particularize the general. A general principle like the pursuit of social justice must be particularized to different situations. The response to a terror regime like that of Saddam Hussein cannot be the same as the civil rights struggle in an American South hemmed in by a federal court system, national guard troops, and an increasingly pro-civil rights Congress and presidency.
In the more customary issues of moral theology, we cannot generalize from the fact that the Church allows natural family planning to the idea that this means that contraception should be allowed. Natural family planning is a particular solution which does not attack the procreative act, but merely abstains from the procreative act at certain times. The particular cannot be thoughtlessly generalized here to excuse contraception.
Rather, in natural family planning, we see the general principle of respecting the procreative act carefully particularized so as to respect the integrity of the procreative act. Natural family planning is an example of the Church particularizing the general in a wise and appropriate manner. So when faced with the facile and tired analogies of pundits or even some moral theologians, remember to ask if they have violated a rule of thumb worth remembering. Have they too easily overgeneralized the particular? Have they failed to particularize the general? Answering such questions is hard because creativity is involved. But that hard analytical work must be done if our opinions are to conform to reality.