Analogy between the priests of the SSPX, and the priests who during the French Revolution swore obedience to the Revolutionary power.
Note that this is not a question of the validity of the sacraments. The swearing priests, as they were called, had been validly ordained and gave valid sacraments, as do the SSPX priests.
But the SSPX, to some extent like the swearing priests, have submitted to the revolutionary authorities: Pope Francis and the diocesan bishops, who are destroying God’s holy Church and sending souls to hell.
No marriage is blessed anymore without the consent of the diocesan bishop, who sends his delegation for the priest to marry the faithful [= he sends his representative to marry], in accordance with the new code of canon law, and making (due to this fact) a profession of modernist Faith.
The newly married couples act do make an act of modernist faith on their wedding day because of the SSPX priest.
And sadly, we can multiply the examples of the rallying of the SSPX to the Conciliar Church.
Here are some extracts from the prescriptions of Pope Pius VI towards swearing priests, in 1798. They apply analogicly to SSPX priests.
General collection of briefs and instructions from Our Most Holy Father Pope Pius VI, Paris, 1798, pp 473-489:
«Answers made by his Holiness, on the advice of a selected congregation of cardinals, to various questions. Although they relate especially to certain requests made to it for particular needs and circuмstances, they can nevertheless be of the greatest use to all bishops and administrators, because in the case of similar difficulties, they would have in this instruction a sure rule, which would give them the most prompt and effective means of helping the faithful in their present necessities, and in the uncertain situation of the churches, would present a form universally agreed upon by all the faithful, as expressed by St. Cyprian. (Cyprian. ep. 32, ed. of Baluze).
I. If it is permitted to the faithful to attend the mass of a parish priest or of any other priest who has taken the civic oath, on days of feast.
II. If it is permitted to the faithful to hear on Sundays and feast days of obligation, the mass of one of the priests mentioned in the preceding article.
III. Whether the faithful may attend the celebration of vespers, and other public prayers, recited under the direction of a parish priest, or any other sworn priest. These three questions have been answered as follows.
The faithful may not attend the holy sacrifice of the mass, celebrated by a parish priest or a sworn ordinary priest, either on feast days or on Sundays and feast days of obligation; nor may they attend vespers and other public prayers, presided over by a parish priest or an
ordinary sworn priest (…) if the faithful were to allow themselves to attend the mass of a sworn priest on a feast day, or on a Sunday, or on a feast day of obligation, or at the celebration of vespers and other public prayers, done under the direction of a parish priest or some other sworn priest, they would certainly be communicating with this priest in a spiritual sense; the consequence is quite simple: the faithful must refrain from attending, either on days of férial, or any other day of Sunday or of feast of obligation, the holy sacrifice of the mass, celebrated by a parish priest or any swearing priest, in the same way to the vespers or to any other public prayer, recited under the presidency of a parish priest or a simple sworn priest.
IV. Fourthly, it is asked whether the faithful can address themselves to their sworn priest to obtain absolution and communion in the course of the year, especially at Easter time.
Answer. No: for the same reasons as above.
V. In the fifth place, it is asked if the faithful can have recourse to their swearing priest for the sacraments of baptism and marriage.
Answer. They cannot do so, except (for baptism,) in the case of absolute necessity, in the absence of any other priest with legitimate powers to confer this sacrament.
VI. Sixthly, it is asked if a Catholic can serve as godfather in the celebration of a baptism administered by a parish priest or another swearing priest.
Answer. Catholics cannot: otherwise it would be communicating in the spiritual order with the schismatic priest.
VII. Seventh. Is it permissible for a member of the faithful to serve as a sponsor in a baptism conferred by an intruding priest?
Answer. No; (same reason).
VIII. Eighth. Can a woman recovering from childbirth present herself before the parish priest or a swearing priest to receive the blessing in the form indicated by the Roman ritual, for the blessing of the recovery? Can she also hear the mass?
Answer. No, because this would be communicating spiritually with schismatics.
IX. Ninth. Can the faithful, at the point of death, or in urgent danger of death, validly receive absolution from a swearing priest, or from an intruding priest?
XI. Eleventh. May the faithful bend the knee in adoration before hosts consecrated by intruders?
Answer. They can, because these hosts really, truly, and substantially contain the body, blood, soul, and divinity of Our Lord Jesus Christ. But in order to avoid appearing to be mixed up with schismatics in this act of religion, Catholics should take care to avoid meeting schismatics in the places where they carry the Blessed Sacrament.»
It is not a question of judging the priests in an individual manner within the SSPX, but by the orientation of the superiors, it is the whole institution that has implicitly sworn allegiance to the revolutionary authorities of the conciliar Rome. So either by commission or by omission the members of the SSPX share in that sin.
To attend their sacraments is on the one hand to encourage them in their choice to remain within the SSPX, on the other hand, it is communicating with their errors and with abandonment of the fight (that is the very reason that is constantly put forward by Pope Pius VI to forbid the faithful access to the sacraments of those priests).