Ever hear people ask that question?
Of course you do. Especially gay people or those who are more or less into - oh what did the old people call it? "Free love"... "What could be more wholesome or natural?"
Almost 40 years ago, back when society was just emerging from horrible, institutionalized, sexual repression,* the Vatican - during the reign of Pope Pal VI, had the audacity to issue an official document entitled Persona Humana - Declaration on Certain Questions Concerning Sexual Ethics.
What's it good for?
One might ask that since it seems to me it has been largely ignored. However the preface does indeed explain why the Church always seems to be talking about sex ...
According to contemporary scientific research, the human person is so profoundly affected by sexuality that it must be considered as one of the factors which give to each individual's life the principal traits that distinguish it. In fact it is from sex that the human person receives the characteristics which, on the biological, psychological and spiritual levels, make that person a man or a woman, and thereby largely condition his or her progress towards maturity and insertion into society. Hence sexual matters, as is obvious to everyone, today constitute a theme frequently and openly dealt with in books, reviews, magazines and other means of social communication.
In the present period, the corruption of morals has increased, and one of the most serious indications of this corruption is the unbridled exaltation of sex. Moreover, through the means of social communication and through public entertainment this corruption has reached the point of invading the field of education and of infecting the general mentality.
In this context certain educators, teachers and moralists have been able to contribute to a better understanding and integration into life of the values proper to each of the sexes; on the other hand there are those who have put forward concepts and modes of behavior which are contrary to the true moral exigencies of the human person. Some members of the latter group have even gone so far as to favor a licentious hedonism.
As a result, in the course of a few years, teachings, moral criteria and modes of living hitherto faithfully preserved have been very much unsettled, even among Christians. There are many people today who, being confronted with widespread opinions opposed to the teaching which they received from the Church, have come to wonder what must still hold as true. - Persona Humana
That makes sense, huh? I strongly urge you to read the whole thing. If you read the documents the Church promulgates, you won't have to depend so heavily upon online evangelists, pop-Catholic authors, or theologically screwed up parish religious ed people.
Included below are a couple of subjects not always taught in Catholic parishes, RCIA, schools, and other places of welcome:
The traditional Catholic doctrine that masturbation constitutes a grave moral disorder is often called into doubt or expressly denied today. It is said that psychology and sociology show that it is a normal phenomenon of sexual development, especially among the young. It is stated that there is real and serious fault only in the measure that the subject deliberately indulges in solitary pleasure closed in on self ("ipsation"), because in this case the act would indeed be radically opposed to the loving communion between persons of different sex which some hold is what is principally sought in the use of the sexual faculty.
This opinion is contradictory to the teaching and pastoral practice of the Catholic Church. Whatever the force of certain arguments of a biological and philosophical nature, which have sometimes been used by theologians, in fact both the Magisterium of the Church - in the course of a constant tradition - and the moral sense of the faithful have declared without hesitation that masturbation is an intrinsically and seriously disordered act. - Persona HumanaHomo. Sexuality.
At the present time there are those who, basing themselves on observations in the psychological order, have begun to judge indulgently, and even to excuse completely, homosexual relations between certain people. This they do in opposition to the constant teaching of the Magisterium and to the moral sense of the Christian people.
A distinction is drawn, and it seems with some reason, between homosexuals whose tendency comes from a false education, from a lack of normal sexual development, from habit, from bad example, or from other similar causes, and is transitory or at least not incurable; and homosexuals who are definitively such because of some kind of innate instinct or a pathological constitution judged to be incurable.
In regard to this second category of subjects, some people conclude that their tendency is so natural that it justifies in their case homosexual relations within a sincere communion of life and love analogous to marriage, in so far as such homosexuals feel incapable of enduring a solitary life. - Persona Humana
The observance of the moral law in the field of sexuality and the practice of chastity have been considerably endangered, especially among less fervent Christians, by the current tendency to minimize as far as possible, when not denying outright, the reality of grave sin, at least in people's actual lives.
There are those who go as far as to affirm that mortal sin, which causes separation from God, only exists in the formal refusal directly opposed to God's call, or in that selfishness which completely and deliberately closes itself to the love of neighbor. They say that it is only then that there comes into play the fundamental option, that is to say the decision which totally commits the person and which is necessary if mortal sin is to exist; by this option the person, from the depths of the personality, takes up or ratifies a fundamental attitude towards God or people. On the contrary, so-called "peripheral" actions (which, it is said, usually do not involve decisive choice), do not go so far as to change the fundamental option, the less so since they often come, as is observed, from habit. Thus such actions can weaken the fundamental option, but not to such a degree as to change it completely. Now according to these authors, a change of the fundamental option towards God less easily comes about in the field of sexual activity, where a person generally does not transgress the moral order in a fully deliberate and responsible manner but rather under the influence of passion, weakness, immaturity, sometimes even through the illusion of thus showing love for someone else. To these causes there is often added the pressure of the social environment. - Persona Humana
Do keep in mind that these documents were issued in the olden days before we were able to grasp the dynamics of conscious evolution and sexual fluidity and genderlessness.*
* (Sarcasm intended.)
A note on Paul VI.
A year after the release of Person Humana the Holy Father underwent a smear campaign claiming he was a homosexual. In a rare response to public libel, the Holy Father denied the accusations and linked them to opposition to the release of the document on sexual ethics, Persona Humana. Story here.
Similar calumnies have been leveled against Archbishop Nienstedt of Minneapolis/St. Paul for his opposition to same sex marriage.