“Chesterton described the sentimentalist as having ‘no honor about ideas; he will not see that one must pay for an idea as for anything else. He will not see that any worthy idea…can only be won on its own terms.’ That nicely describes the modern man who describes himself as ‘spiritual, but not religious.’
The sentimentalist, anxious to denounce and distance [the problems of the Church and the world from] himself, does not stop to consider that the great reformers within the Church—St. Francis, St. Teresa of Avila, St. Catherine of Siena, and others—did not flounce away from what was difficult. They remained, and the profound insights gained through their struggles have instructed and enhanced the ‘worthy idea’ of faith. Dismissing it all with a few overused buzzwords, a sentimentalist runs his premium brain on the cheap and inefficient fuel of superior feeling, but he cannot be accounted a thinker who enhances understanding.” 
The devil is subtle, and part of that subtlety is a solid understanding of the concept of misguided sympathy. There is a tradition among some theologians which says that the devil fell through pride upon seeing it revealed that Christ would be incarnated; a variation of this tradition says that it is not the Incarnation itself which made Lucifer fall, but rather a vision of the passion: “surely there is a better way!” According to this variation, the devil himself fell through pride and misguided sympathy, which I suppose is the subtlest pride of all. Is it any wonder, then, that misguided sympathy is one of his most powerful weapons against the Faith, one of the most alluring temptations which he can use to lead us astray?
I have noticed among my own friends that sympathy for “gay marriage” has not always lead to a complete break with the Church or a complete renunciation of faith. I suspect that for many it won’t happen that way at all, but I suspect that the devil is content to work slowly when haste does not avail him. Sure, many men have been parted from their faith through more direct means: temptations to obvious sins such as adultery and fornication , or to abortion to cover up fornication or adultery or to avoid his own responsibilities when a child is conceived, temptations to drink to oblivion, or to skip going to church on Sunday in favor of sleeping in after the previous night’s drinking and whoring. There are many cases in which some obvious sin of pride or gluttony or lust or wrath is involved, where the starting point is avarice or envy or even simple sloth. Hedonism is a powerful motivator, and always has been, albeit with an ever-changing face. So are desires for wealth and power and honor which reduced other human beings to tools or obstacles, to be used to crushed in pursuit of one’s goal.
Misguided sympathy, on the other hand, is far more subtle, especially when we experience it ourselves. These other temptations might feel good, but I think that few thinking people would call their pursuit in this manner good. Misguided sympathy is a counterfeit so strong as to appear to be the real thing. It seems as if it is the loving thing–and aren’t we supposed to do the loving thing?
The hard truth about love is that it is not easy. It requires of us some sacrifices, sometimes even suffering. Indeed, the very word “sympathy” implies some suffering, as Bishop Fulton Sheen has noted:
“Sympathy is a temper or character which draws others together. It is what might be called conductivity. The Greek origin of the word ‘sympathy’ implies ‘suffering with.’ It is a kind of silent understanding when heart meets heart. It is a kind of substitution, in which one takes the heart out of his own body and places it in the body of another man, and in exchange takes back the other’s heart.”
To be clear, attempts to alleviate suffering are not bad of themselves. Where we can alleviate suffering without doing worse harm to the sufferer, this alleviation can be a good thing, even an act of true charity. I call it an act of charity, though these acts of charity are often known as works of mercy. There are 14 (seven each of spiritual and corporal), many of which have as an effect the alleviation of suffering. It may even be said that the works of mercy alleviate suffering by attempting to fix its causes: by feeding the hungry and giving drink to the thirsty and visiting the sick, or by counseling the doubtful and instructing the ignorant, etc.
However, alleviating suffering is not the only goal—or even really the main goal—of the works of mercy. Rather, these works are to recognize the dignity of the human person, whose ultimate destiny is not suffering, death and sorrow, but rather happiness, eternal life and joy. Thus, real mercy ultimately depends on justice and on human dignity: above all, it relies on charity rooted in truth.
The misguided sympathy which is so often used to undermine the faith looks for a shortcut: to avoid unpleasant truths in the name of alleviating suffering. But this is somewhat akin to treating symptoms while ignoring the disease, and while in the short-term it provides some relief, in the longer term it will lead to greater grief.
Real empathy often underlies misguided sympathy, and there is so often a real desire to help those who are hurting. Thus the deception is made all the stronger, because the break with faith appears to be for noble reasons, as if religion were the cause of the problems. Religion is not the cause, though it is a part of the cure, for the problem is sin. But there is one thing worse than sin, as Bishop Fulton Sheen reminds us: “Sin is not the worst thing in the world; the worst thing in the world is the denial of sin…The denial of sin is the unforgivable sin.”
Misguided sympathy ultimately leaves the sinner where he is: stuck in his sin. It avoids the responsibility, not merely of looking for relief from suffering, but of uplifting the sufferer and helping him to his higher end. For while suffering is bad, it can be turned to a good end, and from sorrow can come wisdom, and out of suffering can come joy. Even suffering can be embraced and then sanctified and the sufferer redeemed, but sin can only be rejected.
Real love, charity in this case, is inseparable from truth. It risks sacrifice even while it looks to relieve the suffering of the other. This relief may come from the sacrifice of taking on the other’s suffering as one’s own, but it cannot be separated either from the truth of the human person and the human condition. Misguided sympathy mistakes the wideness of God’s mercy for a wide path to tread towards our final destination. It ignores the ultimate Truth upon which all other truth is finally based, and so misses the narrow path which leads through suffering and sorrow, until finally finding joy.
There is another tragedy involved with misguided sympathy. As I said before, underlying misguided sympathy is often real empathy, a real desire to to help those who are suffering, a real desire to show kindness to others. These are all good things, they are all components of real sympathy, and us of real love, that is, of charity. But when they are opposed to truth via misguided sympathy, they become twisted and distorted: they may show kindness to the the “victim” (e.g. a friend with same-sex attraction) at the expense of resenting the Church (which includes her fallen members as well as her infallible teachings). This, in turn, causes a scandal (temptation to sin) for the Church’s members, for they then see that instances of kindness towards sinners are followed by instances of rejection o the Church, and are thus themselves presented with a false dichotomy between kindness on the one hand and obedience–and really, faith–on the other. The Church is therefore not only deprived of some faithful witnesses of real love in action–a synthesis of faith, hope, and charity–but is also provided with a counter-witness of kindness opposed to faith, as if faith and charity could work against each other.
That same witness is then provided to the culture at large, which is (as it often is) at least a little bit hostile to the Church. In the case of the genuine witness of love rooted in truth, the culture gets evangelized. On the other hand, in the counter-witness of kindness opposed to faith, the culture gets anti-evangelized, that is, it gets turned away from the Church, and gets an excuse eventually to persecute the Church. We have been there before many times, and in many places: the culture needs no such pretexts.
What the culture needs, and what the Church herself needs, is the witness of the saints, here and elsewhere. The saints are, after all, the mirrors of Christ (cf 1 Corinthians 13:12). As for real sympathy, I think it is well-captured in one of the poems of Saint John of the Cross, entitled “The Young Shepherd”:
A lone young shepherd lived in pain
withdrawn from pleasure and contentment,
his thoughts fixed on a shepherd-girl
his heart an open wound with love.
He weeps, but not from the wound of love,
there is no pain in such affliction,
even though the heart is pierced;
he weeps in knowing he’s been forgotten.
That one thought: his shining one
has forgotten him, is such great pain
that he bows to brutal handling in a foreign land,
his heart an open wound of love.
The shepherd says: I pity the one
who draws herself back from my love
and does not seek the joy of my presence,
though my heart is an open wound with love for her.
After a long time he climbed a tree,
and spread his shining arms,
and hung by them, and died,
his heart an open wound with love.
 From Elizabeth Scalia’s essay on Sentimentalism, found in Disorientation: The 13 “Isms” That Will Send You to Intellectual “La-La Land”.
 Or to unnatural sexual relationships, which include those in which both partners are of the same sex.