Feel free to grant the benefit of the doubt, but at times doing so is to ignore a bit of the reality. There is lots of history here, and this Bishop has a temper. The suggestion he is doing this silencing for the benefit of the priest is BS.
Perhaps the bishop is preventing Fr Altier from being in a position to be a vocal opponent of his policy, thus safeguarding his promise of obedience. Perhaps he is preserving Fr Altier from giving scandal and fostering hostility toward legitimate authority. Perhaps he is preventing Fr Altier's words from motivating an agenda contrary to the spirit with which the words were spoken. There are a number of valid reasons that the bishop may exercise his perogative. Unless the bishop is behaving in a manifestly immoral way, we must accept his decisions. Fr Altier, it seems, has.
I don't even think (despite the fac that I wrote earlier) that we should give him the benefit of the doubt. The bishop has the right to more than that. It is not a question of the benefit of the doubt. It is a question of divinely constituted authority.
By the way, I am a fan of Fr Altier. So I do not write this as a backhanded attempt to smear him in any way. I have friends who have been very strengthened in faith because of having heard his homilies. I hope that a Fr Altier fares well despite the pain that fidelity to his solemn promise may engender.