On second thought, this action was not surprising. Fiorenza was probably getting pressure from other bishops to make an example out of Zigrang to deter other priests from instruction by SSPX. The traditional movement is growing. The bishops can no longer ignore it. Something must be done to stop it.
You have an extremely exaggerated sense of the importance of your movement. The Eastern Orthodox "traditional" movement has hundreds of millions of members and has lasted a thousand years. In a like manner, the Oriental Orthodox, who reject the "pseudo-synod" of Chalcedon, continue to preserve their "tradition" in far greater numbers than the SSPX, and have done so for 1500 years. The Catholic Church is threatened by neither.
Or rather this criterion may stand in need of more exact definition. For the universality which carries weight here is, as Vincent of Lerins says, that "of the true disciples, the true adorers, of Christ", or, to use the Gospel image, of the true sheep of Christ. Will they be recognizable by some sign distinguishing the true faithful from the false? Undoubtedly they will, granted that Christ confided His sheep to Peter, that He set Peter over His Church, and commanded him to confirm his brethren in the faith. The true faithful will be found amongst the faithful gathered round Peter; the true universality will be that of which Peter is the centre; where Peter is, there will be the Church.[1117] The criterion of universality will then attain that strictness which the progress of our time makes desirable. And thus the argument from universality taken as a sign of apostolicity will receive its final touch from the Gospel prophecies concerning Peter; the quod ubique, quod ab omnibus is given its last precision by the quod ab Ecclesia romana. In this way the via apostolicitatis leads into the via primatus. And we may see a sign of it in the fact that St. Augustine, who had so often appealed to the universality of the true faith against the heretics, was himself, after St. Ambrose's example, expressly to invoke the authority of Rome against the Pelagians: the resolutions of the Councils of Carthage and Milevis, he says, "have been sent on to the Apostolic See. Decisions have come from thence. The cause is ended. May it please God to end the error."[1118]1117 "It was to Peter that Christ said: Thou art Peter, and on this rock I will build my Church. Where therefore Peter is, there is the Church: where the Church is, there is no death but eternal life. That is why He added: And the gates of hell shall not prevail against it; and I will give unto thee the keys of the kingdom of heaven. Blessed Peter, against whom the gates of hell have not prevailed, for whom the gates of heaven are not closed, but who, on the contrary, has destroyed the antechambers of hell and opened the heavens! Standing on the earth he opens heaven and shuts hell" (St. Ambrose, Enarr. in Psalm., XL, 30; P. L. XIV, col. 1082 ).
1118 Sermo CXXXI, 10. (Journet, The Church of the Word Incarnate)
Father Zigrang was disobedient... and therefore should have been made an example of.