It is unclear how depriving "a stable group of faithful" of their preferred rite is either fair or prudent in this case. It would be helpful if the bishop would explain his reasoning.
Although I am not certain, I have a sense of what appears to be going on, though additional evidence could change my mind.
Both the Tridentine and Novus Ordo are licit forms of the Mass. However, to offer the Tridentine Mass publicly requires a few extra steps, so to speak.
Unity is a requirement of the Church, and any intentionally actions to create disunity are forbidden.
Having read some comments about the Franciscan case, and now this case, a concern mentioned was that those offering the Tridentine Mass were using the form as a sort of protest, almost a passive-aggressive statement.
If, and a big if, that is the case, it would make sense for the local ordinary to forbid it use, by the “offending” parties, though not for the diocese as a whole.
Alternatively, if the bishop just doesn’t like the Tridentine Mass and is forbidding it for non-Canonical reasons, that is a different story.
Generally speaking, however, I tend to side with the local ordinary, as he bears the greater responsibility and is also to be afforded obedience.