From what I understand, it started as explained above, with back and forth about the Thesis. Then it escalated over the Jab. Bp Dolan was very vocally against the clot shot, and Bp Sanborn basically said that as clergy, they should stay out of it since they aren't medical experts. And rather than call each other on the phone to work things out, they both decided to trade shots on Twitter, in their respective bulletins, on their websites, and with YT videos. All extremely public, unnecessary, and unfortunate. I think someone mentioned in another thread that Bp Dolan and Bp Sanborn were never all that close, but Fr Cekada was the mediator keeping good relations between them, and all of this public fighting really spilled over after Fr C's death.
I agree that with each passing year/decade the Thesis becomes more difficult to defend. Pure speculation and personal opinion here, but I think Bp Sanborn's zealous clinging to the Thesis is primarily due to the fact that he comes from the Des Lauriers line. So, when people criticize the Thesis, he feels he more compelled to defend it. Again, just my opinion.
It is so sad to see these needless public squabbles. We already have much to suffer through in this crisis without all of this drama. To his credit, Bp McGuire has handled all of this very well (IMHO) since taking over at SGG. He instructed his clergy to no longer engage in social media debate about the Thesis. I pray that in time, all of the needless Sede disputes of the past can be put aside, and common ground be found to the benefit of the faithful. Perhaps Bp Pivarunas can invite SGG, RCI, SSPV, etc to the annual Fatima conference and they can hash out some things and bring some unity to the Sedes. I pray
