It seems to me that the Bishop’s sin is the greater here. The priest seems to be an unrepentant heretic who is simply doing what he believes, ugly and sad as that is. However, it is obvious that the bishop has known about this for some time, probably years from what I gather, and has done nothing at all beyond writing a couple of letters. I find it hard to believe that if he saw someone stealing his car he would be this lax in a response, but would act immediately and demand that others do as well. But here we see a man leading numerous souls astray and acting to sow schism in the Church, and the bishop, who admits to knowing that the actions of the priest are wrong, is simply sitting idle while people may actually be dragged down to hell. As bad as the priest is it is bishops of this sort that actually bear the responsibility for these errors and heresies.
Lends credence to the quote: "The road to Hell is paved with the skulls of bishops".