Yesterday, a very interesting comment was left on a previous post, and I would like to respond to it here because something of what Pope Benedict says in the beginning of his encyclical helps to answer this question. The comment was:
What is the basis for you assuming that homosexuality is morally wrong? Abortion and guns brings obvious harms to society whereas homosexuality does not. This is so clear that even teens can see it. Please explain yourself.
This is a good question, and I am glad it is worded the way it is. This individual calls the harms that guns and abortion bring "obvious" and "clear" while at the same time
A basic precept of morality is that every action has an effect on another person, particularly when that action is sinful. Homosexual relationships are considered sinful because they are a prevision of the good of sexual relations, which are meant for the purpose of procreation of children and union of spouses. When two men or two women engage in sexual acts without the commitment of marriage or the common goal of procreation, they are using their sexuality in an improper way. Thus, there is no way that their relationship can be a good for themselves or the other.
Pope Benedict says the following in paragraph 5 of his new encyclical; though long-winded, it is a fitting explanation of the respect that must be given to the body and the proper purpose of sexuality.
Nowadays Christianity of the past is often criticized as having been opposed to the body; and it is quite true that tendencies of this sort have always existed. Yet the contemporary way of exalting the body is deceptive. Eros, reduced to pure “sex”, has become a commodity, a mere “thing” to be bought and sold, or rather, man himself becomes a commodity. This is hardly man's great “yes” to the body. On the contrary, he now considers his body and his sexuality as the purely material part of himself, to be used and exploited at will. Nor does he see it as an arena for the exercise of his freedom, but as a mere object that he attempts, as he pleases, to make both enjoyable and harmless. Here we are actually dealing with a debasement of the human body: no longer is it integrated into our overall existential freedom; no longer is it a vital expression of our whole being, but it is more or less relegated to the purely biological sphere. The apparent exaltation of the body can quickly turn into a hatred of bodiliness. Christian faith, on the other hand, has always considered man a unity in duality, a reality in which spirit and matter compenetrate, and in which each is brought to a new nobility. True, eros tends to rise “in ecstasy” towards the Divine, to lead us beyond ourselves; yet for this very reason it calls for a path of ascent, renunciation, purification and healing. (p. 5)
"Exploited at will," the Holy Father says. Sexuality has thus become an object that is not seen as a good, but only as a means to the end of arousal and passion. No thought is given to the demand for commitment (marriage) or the natural, biological good of children (procreation).
Through this disrespect of the body (both of self and other), man "himself becomes a commodity." This is precisely what homosexuality does to man: makes him a "commodity."