Why is a priest able to obtain dispensation from his vows and a married person can't? That's unfair!
No error in the choice of a life companion is acceptable in the eyes of the Church. Now, what about priests, monks and nuns who give up their vocation? Have they not contracted a kind of marriage with the Lord? Is God's Spirit so selective in the choice of His children?
In some cases, it is possible to obtain a declaration of nullity of marriage. If one thinks that, at the time of his or her marriage, some psychological reasons or an evident absence of maturity could have prevented the marriage from being valid, he or she should consult a priest. A Church matrimonial court will make the necessary inquiries, question the parties involved and their witnesses, then, after earnest deliberation, decide whether the marriage was valid or not. On the other hand, let us not forget that the new Code of Canon Law has restricted the possibilities for monks and nuns to be dispensed from their vows and also that these vows, contrary to marriage vows, are not a sacrament.
I cannot say if specific religious persons, who have been dispensed from their vows, were guilty of infidelity. I would have to know the reasons, the motives why they quit. You say it is the same in the case of married people who divorced. No one can tell if they were subjectively guilty. That is true! But, once again, in the case of marriage we deal with a sacrament instituted by Christ, a sacrament that is and must remain the symbol of a perfect love.
There is also the case of a priest who can obtain his secularization. First, let me tell you that he does not get it easily. Second, for him as for monks and nuns, it is a question of his vow of chastity, which is not a sacrament. He is not dispensed from the sacrament of priesthood. He remains a priest. He is just dispensed from the obligation to observe celibacy. In ordinary circumstances, the Church requires that he cease exercising his priestly ministry.
Quibbling? Sophistic reasoning? Theological subtleties? Yes and no! The doctrine is clear. It is up to us to try and understand the Church's standpoint with regard to this or that state of life.
It is the Lord who probes the mind and the heart (Jr 20: 12). Only He can know if a spouse, a nun, a monk or priest has been guilty of infidelity.
We cannot judge consciences. Let us rely on the Spirit who guides the Church toward respecting both Christ's doctrine and His mercy. Neither one can be sacrificed. They have to be reconciled! That is the delicate task of the Church's pastors.