Your rejection of “moral unity” has no basis in any magisterial document.
Nor has the Church taught that such acts of foreplay (as explained by such as Dr. Grisez) are evil. Nowhere.
In fact your argument would in the end be saying too that kissing in an arousing way…before actual intercourse …say even for a good 15 minutes prior …is a non-unitive- non-procreative sexual act and thus is evil.
The term ‘moral unity’ is essentially the same as ‘the principle of totality’; both terms attempt to group a set of acts together, and to justify one act by the fonts of morality of a different act. Humanae Vitae rejects this approach.
Pope Paul VI as the question as to whether a set of sexual acts within marriage can be justified if only some of the acts are unitive and procreative:
“Moreover, if one were to apply here the so called
principle of totality, could it not be accepted that the intention to have a less prolific but more rationally planned family might transform an action which renders natural processes infertile into a licit and provident control of birth?
Could it not be admitted, in other words, that procreative finality applies to the totality of married life rather than to each single act? A further question is whether, because people are more conscious today of their responsibilities, the time has not come when the transmission of life should be regulated by their intelligence and will rather than through the specific rhythms of their own bodies.” (HV, n. 3)
Pope Paul VI then answers the question, rejecting this idea of grouping sets of acts together:
“The Church, nevertheless, in urging men to the observance of the precepts of the natural law, which it interprets by its constant doctrine, teaches that
each and every marital act must of necessity retain its intrinsic relationship to the procreation of human life. This particular doctrine, often expounded by the magisterium of the Church, is based on the inseparable connection, established by God, which man on his own initiative may not break, between
the unitive significance and the procreative significance which are both inherent to the marriage act.” (HV n. 11-12).
Therefore, sexual acts which lack the unitive or procreative meanings are not moral. They are not justified by being followed by, or preceded by, a natural marital act, because each and every marital act, each single sexual act, must be procreative and unitive, as well as marital.
Kissing and hugging and other acts which are arousing, but which are not a use of the sexual faculty, need not be unitive and procreative, because these are not sexual acts.
The Magisterium teaches in the above quoted text, that each single sexual act must be unitive and procreative. It is absurd to claim that a non-unitive or a non-procreative act, condemned by the Church, becomes moral by being renamed ‘foreplay’. It is equally absurd to claim that the principle of totality, rejected by the Magisterium, becomes true by renaming it ‘moral unity’.