I have been writing this month on the Manhattan Declaration - a document outlining a set of principles on matters of life, marriage, and religious liberty.
The Declaration contains the following line:
To strengthen families, we must stop glamorizing promiscuity and infidelity and restore among our people a sense of the profound beauty, mystery, and holiness of faithful marital love.
On this, the Manhattan Declaration is correct.
Of course, I would not put it in those same terms. In desire utilitarian terms, we have many and strong reasons to promote an aversion to promiscuity and infidelity, and to promote stronger desires for tight marital bonds between individuals.
A basic long-standing objection against adultery is that it involves the breaking of a promise. The wedding vow itself is a promise not to sleep around with others. A person who then has sex with violates that promise and this, in itself, involves doing something that no good person would do.
But what do we say about the people who never make such a promise? They enter into a marriage in complete agreement that each may have sex with others, No promise is done, so there is no wrong.
Another way of stating the issue with respect to adultery is that it is not a question of whether a promise, once made, should be kept. It is a question of whether the promise should or should not be made - what the promise (or the lack of a promise) itself says about the moral character of the individual.
The desire utilitarian case against adultery is that people have many and strong reasons to praise those who make (and then to keep) a promise a marital (or relationship) fidelity, and to condemn those who engage in sex without that fidelity - engage in promiscuous and adulterous behavior.
A large portion of those many and strong reasons comes from the many and strong reasons we have to prevent the spread of disease, and the desire-thwarting that those diseases bring. We get many of these reasons from preventing the spread of disease such as syphilis and AIDS. Recent medical research is showing that many forms of cancer - cervical, pancreatic, oral, anal, and even potentially some breast cancers - are cause by the spread of sexually transmitted viruses.
(See: Stanford University series on Darwin's Legacy Lecture 8)
We have many and strong reasons to hope that we, ourselves, do not get these diseases. We have many and strong reasons to hope that those we do not care about get these diseases, We should have many and strong reasons to hope that we can keep these diseases out of the future of any child's life. So, we have many and strong reasons to promote strong desires for extended monogamous relationships, and to condemn those who are promiscuous or adulterous - as well as those who promote and glorify promiscuity and adultery.
We have many and strong reason to hold that those people who make a promise of marital fidelity and keep that promise are better people - far better people - then those who show those values that have in the past and will continue to contribute to the spread of these diseases and the desire-thwarting that result from them.
These points argue that there is a virtue in promoting institutions, norms, and policies that have the effect of encouraging long-term monogamous relationships and of discouraging those things that tend to break marriages apart.
This idea of promoting desires that tend to fulfill other desires and inhibit desires that tend to thwart other desires (such as promoting an aversion to promiscuity and adultery and promoting a desire to be in a long-term monogamous relationships) is one that has to take the scientific facts into account. People like to imagine all sorts of harms and benefits circulating around the fulfillment of their own desires.
While abstinence-only sex education is certainly consistent with promoting an aversion to promiscuity and (later) adultery, we cannot ignore the evidence that says that this option is so drastically opposed to our biological natures that the attempt does more harm than good. We get more disease, more misery, and more death trying to teach abstinence then we would get by supporting long-term, mutually caring, relatively safe monogamous relationships.
If you wish to absolutely avoid any chance of getting in an automobile accident then this can be done by totally abstaining from ever getting into a car or being near a road. However, insofar as this is completely impractical, the next best option is to teach people to drive safely.
Consistent with all of this is the fact that those who oppose homosexual marriages are the true enemies of marriage itself. The many and strong reasons we have for promoting long-term monogamous relationships are reasons for promoting long-term monogamous relationships among both homosexuals and heterosexuals alike. Our institutions should be (a moral person would insist that they are made to be) just as strongly supportive of the long-term monogamous homosexual relationship as it is of the long-term monogamous heterosexual relationship.
People who are not supportive of long-term homosexual relationships through the institution of homosexual marriage have placed themselves on the side of promiscuity, disease, misery, and death instead. In at least this part of the lives, they bring evil into our society, and the suffering that comes along with it. If they are unable to see the evil that they do, it is because their prejudices and bigotry as well as their own egos refuse to admit the vicious truth of what they do.