I am sure the information on sedevacantists applies here as well, as each has a dark character and leads to schism.
This is from www.sspx.ca, the December 2004 link.
Spiritual illness of Sedevacantism:
How could we understand the state of a Sedevacantist mind? I think it is characterized by a fixed idea, which is almost an obsession. Their mind seems to freeze on the problem of the pope, which appears to them as being very serious and urgent. This is a typical case of Intellectual Desolation, by which their soul is being disturbed as long as a 'clear answer' has not been found for such a serious problem. Sedevacantists claim that it is urgently needed to make a judgment on the Vatican II popes. For them, it appears to be THE fundamental problem all Traditional Catholics should focus on. For example, let me quote Bishop Pivarunas: "As unpleasant as this subject may be, traditional Catholics are confronted by the terrible and burning questions: Is the Conciliar Church the Catholic Church? Is John-Paul II, as the head of the Conciliar Church, a true pope?…Suffice it to say, the issue of the pope is a difficult one, and unpleasant one, and a frightful one; yet it is a necessary and important issue which cannot be avoided." Let me summarize how Sedevacantists approach the question of the pope: #1 it is a question they have at heart; #2 they want to get a final answer with absolute certainty; #3 such problem is so urgent that it becomes the focus of their attention, up to the point that they cannot see anything else. Thus, they direct their arguments not much against the Modern Church, for which they care less, but against those fellow Traditional Catholics who do not share their conclusions. St. Francis de Sales suffered similar Intellectual Desolation. It was on the matter of predestination. His intellect froze on that question, and his heart was filled with the anguish that he may be damned no matter what. The more he was studying, the more he was finding serious objections against predestination. This was driving him nuts. How did St. Francis manage to free himself from that intellectual prison? One day, he fell on his knees before a statue of Our Lady and said: "O Holy Virgin, I think that I am going to be damned. If I have to curse God for all eternity, let me at least offer you this day in honor of God." When St. Francis de Sales got up, he was healed, being able to relocate his 'problem' at the second place, which is after the humble fulfillment of his daily duty. Let me apply that example to the sedevacantist bug: "Who knows if John-Paul II is pope? Who knows if the Society of St. Pius X is schismatic, as they recognize the pope, and don't obey to him?" In a Sedevacantist mind, such questions are producing deep emotional reactions, which lead to anger and panic: the Sedevacantist is looking for a final answer right now. This kind of Intellectual Desolation is very dangerous. It is threatening pious souls, who are being convinced that they would betray their consciences if they were to ignore these fundamental issues. Such problem affects persons tempted to intellectual pride, and having a tendency to look for the most extreme and desperate solutions, like Brother Michael Diamond, from Most Holy Family Monastery.
In the book of the Spiritual Exercises, St. Ignatius of Loyola gives some rules for Discerning the Spirits. Here are the ones that should be used to deal with the Intellectual Desolation of Sedevacantists: do not make any change to your previous resolutions (5th rule); counter attack the temptation, by prayer and penance (6th rule); make an act of will by which you will refuse to be locked in a controversy that you are not qualified to settle (12th rule). You need to practice intellectual self-discipline and mortification of the will, in other words humility. In our daily life, there are many problems which we are unable to settle, because we do not have the tools. Let us humbly recognize it. Moreover, I think it is important to de-passionate and de-dramatize the problem of the pope: when you will appear before him, do you think that St. Peter will ask you for your opinion on one of his successors? Let me be clear: I do not want to evacuate the real problem of the Church since Vatican II, but to give some simple rules of intellectual self-discipline in order to de-dramatize the Sedevacantist issue, which appears very clearly to be a case of Intellectual Desolation. Always remember that the devil is a liar. He is using the Sedevacantist bug to draw some pious souls away from the means of sanctification, the Mass and the Sacraments. Beware!