Christopher West lied about the position of Saint Alphonsus Liguori on a particular sexual act, which is inaccurately and euphemistically called marital foreplay. In his book, At the Heart of the Gospel, West writes:
“And here my teaching is closer to that of St. Alphonsus Liguori than to that of Jone and Merkelbach. Liguori condemns such behavior not because it contradicts the inherent orientation of ejaculation. Rather, Liguori believes such behavior cannot happen ‘without sodomitic emotion’ (TM 6.469). In other words, he believes spouses who engage in this behavior demonstrate a serious distortion in their emotional dispositions, as do I.” 
I just looked up the reference West gives, Saint Alphonsus Liguori, Moral Theology, Book 6, n. 469. It does not say “without sodomitic emotion”. There is no phrasing even close to those words. There is no assertion with even a remotely similar meaning.
The question, given number 469, is whether it is a type of incest for persons who are related by blood or affinity to commit sodomy. The most probable answer, says the Saint, is that any type of sexual intercourse (coitus) is incest between persons who are so related, whether it is natural or unnatural. He also says that, even when this sin is committed between married persons, it is a mortal sin and they have to confess it in Confession.
Saint Alphonsus Liguori does not say anything like “without sodomitic emotion”. He does not approve of the use of consummated or non-consummated sodomy, nor any other unnatural sexual acts, with or without climax, within marriage. And he never states that his reason for rejecting this act is that the act is always accompanied by “sodomitic emotion”. Rather, he clearly states that the act is unnatural.
So when Christopher West says that his position on marital sodomy is closer to that of Saint Alphonsus Liguori, he is lying. The holy Saint utterly condemns all of the unnatural sexual acts that West finds to be permissible (whether he favors the act or not). The Saint does not permit these acts as long as climax is lacking, nor as long as climax occurs later, during the natural act. And he does not permit climax for the wife outside of the natural marital act.
I’ve seen this claim about Saint Alphonsus Liguori permitting unnatural acts, as long as the “sodomitic emotion” is avoided, in other places online. That false claim is spreading via the internet. He never wrote anything of the kind. Merkelbach is the one who made that claim, not Saint Alphonsus Liguori.
West’s “teaching” is contrary to what Saint Alphonsus Liguori taught. The Saint is the Church’s greatest moral theologian. St. Alphonsus condemns using a disordered orifice (which could refer specifically to anal sex, or more generally to any type of sex other than the natural act).
“Whether it is a mortal sin for the husband to begin copulating in a disordered [or perverse] orifice, then afterward consummate the act in the proper orifice?”
Saint Alphonsus Liguori answers in the affirmative. It is a mortal sin.
“The reason is that this manner of his sexual act (even without climax) is truly sodomy, whether or not it is consummated, just as an act of copulation in the natural orifice of another woman is truly fornication, even if there is no climax.”
“And besides, whenever another orifice [or vessel] is sought by the husband, other than the natural orifice, which has been ordained for copulation, it is considered [to be] an abnormal type of [sexual] pleasure.” 
So the teaching of Saint Alphonsus is not the same as what West teaches, but rather the opposite.
And what West teaches also contradicts what Pope Pius XII taught. For the Pope condemned any sexual acts to climax, outside of the natural marital act, for the wife as well as for the husband.
Pope Pius XII: “What has been said up to this point concerning the intrinsic evil of any full use of the generative power outside the natural conjugal act applies in the same way when the acts are of married persons or of unmarried persons, whether the full exercise of the genital organs is done by the man or the woman, or by both parties acting together; whether it is done by manual touches or by the interruption of the conjugal act; for this is always an act contrary to nature and intrinsically evil.” 
It is not moral for the wife to use any type of act whatsoever, so as to climax outside of the natural marital act. Even when this climax occurs immediately after the natural act, by its interruption, or beforehand by manual touches, it is nevertheless “always an act contrary to nature and intrinsically evil.”
Yes Christopher West and Gregory Popcak and others all claim that the wife is under a different set of rules, and that she can reach climax by any means (even sex toys), outside of the natural act. And they are writing this claim many years after the Magisterium, in the teaching of Pope Pius XII, taught the contrary. How do they get away with contradicting the teaching of Saints and the Church? They lie.
Gregory Popcak lies. First, he tells a pornographic story about “Philip” and “Elizabeth” using sex toys to cause the wife to climax outside of the natural marital act. Then Popcak claims: “It may surprise you to know that, at least as their relationship is described above, it’s not 100 percent clear that Philip and Elizabeth are technically doing anything that violates Catholic sexual teaching.” 
Yes, that does surprise me, mainly because I’ve read teachings to the contrary by Saint Thomas and Saint Alphonsus, and by the Magisterium. So, it is 100% clear that the fictional couple are violating the natural law by a mortal sin.
Seeking the climax of the wife outside of the natural marital act is “always an act contrary to nature and intrinsically evil”. And that is a teaching of the papal Magisterium. Furthermore, in my book, The Catholic Marriage Bed, I explain other teachings of the Magisterium which combine to condemn all of these unnatural sexual acts in marriage (chap. 5).
In another book, Good News about Sex and Marriage, Christopher West again claims that anal foreplay is not necessarily always immoral:
“Perhaps in some abstract, objective sense there is nothing to condemn mere penetration of the anus as absolutely and in every case immoral. But subjectively speaking, for all of the above reasons it is very difficult to justify anal penetration as a loving act of foreplay to the marital embrace. It is an act that seems to stem much more from the disorder of lust than from a genuine desire to symbolize and renew the marriage commitment.” 
Wrong. Unnatural sexual acts are always contrary to nature and intrinsically evil. When an act is intrinsically evil, it is, by that very fact, “absolutely and in every case immoral”. It does not matter how the act seems “subjectively”. The act is wrong no matter whether it stems from a good or bad motivation.
Pope Saint John Paul II on intrinsically evil acts:
“The negative precepts of the natural law are universally valid. They oblige each and every individual, always and in every circumstance. It is a matter of prohibitions which forbid a given action semper et pro semper [always and in each instance], without exception, because the choice of this kind of behaviour is in no case compatible with the goodness of the will of the acting person, with his vocation to life with God and to communion with his neighbour. It is prohibited — to everyone and in every case — to violate these precepts.”
Unnatural sexual acts are not moral to use within marriage, regardless of the circumstances, regardless of the intention, and regardless of which other acts are chosen before or after the unnatural act. The promotion of unnatural sexual acts in marriage is a result of the influences of sinful secular society on us poor fallen sinners. But the result is the pornification of the Sacrament of holy Matrimony.
* Saint Alphonsus Liguori on Marital Chastity
* Saint Thomas Aquinas on Marital Chastity
* Pope Pius XII, Address to the Second World Congress on Fertility and Sterility
* The Catholic Marriage Bed
* Catholic Answers Apologist Trent Horn on Sex Toys in Marriage
Ronald L. Conte Jr.
Roman Catholic theologian
 West, Christopher. At the Heart of the Gospel: Reclaiming the Body for the New Evangelization (p. 228). The Crown Publishing Group. Kindle Edition.
 Saint Alphonsus Liguori, Moral Theology, Book VI, n. 491-2.
 Pope Pius XII, Address to the Second World Congress on Fertility and Sterility, n. 25.
 Popcak, Gregory. Holy Sex!: A Catholic Guide to Toe-Curling, Mind-Blowing, Infallible Loving (p. 194). The Crossroad Publishing Company. Kindle Edition.
 West, Christopher. Good News about Sex and Marriage: Answers to Your Honest Questions about Catholic Teaching (Kindle Locations 1903-1907). Servant. Kindle Edition.