Vatican I taught -- infallibly -- that the Pope is only infallible under certain conditions. (Decree: Pastor Aeternus) No "rationalization" is required; it's clearly spelled out.
I think you have missed my point. Regardless of when the Pope is "infallible" - and I do not concede that he is - ALL faithful Catholics are mandated to be in subjection and obey the Pontiff as he is in persona Christi (in the person of Christ). From http://en.wikipedia.org/wiki/In_persona_Christi:
Bishops of Vatican Council II (1964)2: 28. … Priests, although they do not possess the highest degree of the priesthood, and although they are dependent on the bishops in the exercise of their power, nevertheless they are united with the bishops in sacerdotal dignity. By the power of the sacrament of Orders, in the image of Christ the eternal high Priest, they are consecrated to preach the Gospel and shepherd the faithful and to celebrate divine worship, so that they are true priests of the New Testament. Partakers of the function of Christ the sole Mediator, on their level of ministry, they announce the divine word to all. They exercise their sacred function especially in the eucharistic worship or the celebration of the Mass by which acting in the person of Christ… 29. At a lower level of the hierarchy are deacons, upon whom hands are imposed “not unto the priesthood, but unto a ministry of service”.
Pope Paul VI (1967)3: 29. … acting in the person of Christ, the priest unites himself most intimately with the offering, and places on the altar his entire life, which bears the marks of the holocaust.
Pope John Paul II (1980)4: 8. The priest offers the holy Sacrifice in persona Christi… Awareness of this reality throws a certain light on the character and significance of the priest celebrant who, by confecting the holy Sacrifice and acting “in persona Christi,” is sacramentally (and ineffably) brought into that most profound sacredness, and made part of it, spiritually linking with it in turn all those participating in the eucharistic assembly.
Typical Version of the Catechism of the Catholic Church (1997)5: 875: … No one can bestow grace on himself; it must be given and offered. This fact presupposes ministers of grace, authorized and empowered by Christ. From him, bishops and priests receive the mission and faculty (“the sacred power”) to act in persona Christi Capitis; deacons receive the strength to serve the people of God in the diaconia of liturgy, word, and charity, in communion with the bishop and his presbyterate. The ministry in which Christ's emissaries do and give by God's grace what they cannot do and give by their own powers, is called a “sacrament” by the Church's tradition. Indeed, the ministry of the Church is conferred by a special sacrament.”
Pope Benedict XVI (2007)6: Celebrating the Chrism Mass on Holy Thursday with the priests of Rome, Pope Benedict XVI said that priests should prepare themselves thoroughly to celebrate Mass and administer the sacraments, remembering that they act in the person of Christ.
Code of Canon Law (1983)7 as modified by Benedict XVI (2009)8: Can. 1008 By divine institution, some of the Christian faithful are marked with an indelible character and constituted as sacred ministers by the sacrament of holy orders. They are thus consecrated and deputed so that, each according to his own grade, they may serve the People of God by a new and specific title. Can. 1009 §1. The orders are the episcopate, the presbyterate, and the diaconate. §2. They are conferred by the imposition of hands and the consecratory prayer which the liturgical books prescribe for the individual grades. §3. Those who are constituted in the order of the episcopate or the presbyterate receive the mission and capacity to act in the person of Christ the Head, whereas deacons are empowered to serve the People of God in the ministries of the liturgy, the word and charity. The change in Canon Law introduced by Ominum in Mentum resolved a discrepancy between the applicability of in persona Christi Capitis (“in the person of Christ the Head”) to deacons as well as priests and bishops. With the new Motu Proprio, in persona Christi Capitis applies only to priests and bishops.
If such power and authority is given to priests and bishops, how much more the leader, the Pope? As we have seen discussed the last year since the new Pope Francis was named, there is dismay expressed by some Roman Catholics over his seeming liberal bent. No doubt, this is not the first time the head of the Catholic church has caused questions and his actions bring doubt. Yet, ALL Christians are supposed to be in subjection to him - at least that's what past popes have "infallibly" stated. When Vat I taught that dogma, NOBODY qualified its meaning as only being applicable to ex cathedra conditions but everything he declares is to be obeyed. Catholics aren't supposed to use their own personal interpretations in this case.