"Objectively self-serving scheme"? That is purely a subjective judgment on your part.
I'm not convinced the anti-una cuм position is true or an error. Just because the Church has never had to deal with a similar situation doesn't mean it's an error.
Who's to say that assisting at a mass una cuм a heretic "pope" for decades is not a danger to one's soul? Where are the "fruits" of the una cuм SSPX? Perhaps doing so for decades tends towards eventual compromise with the Devil.
1. No, whether or not it's justifiable or good, objectively it serves the person who promotes it. That just is what it is. Now he might not INTEND that "self serving" but rather some higher motive -- but still, objectively, he's getting the benefit. That's what I mean by "objectively". We can only argue about whether or not he's JUSTIFIED in promoting the teaching, and whether or not his motives are base. We could also debate whether or not he willed that benefit as the PRIMARY motive, or a mere side effect of preaching "the truth". But the GOOD HE RECEIVES by promoting such a teaching? That's really beyond debate. Pure common sense.
But again, even if he were just "preaching the truth",
he still SHOULD KNOW BETTER, see #3.2. Even other sedevacantists didn't dare "go there" until Fr. C stepped up. Keep that in mind.
3. Who's to say? Certainly not Fr. Cekada. He is binding the souls of his Faithful to his own personal opinions and views. He is elevating his opinions to the level of dogma, and then binding his Faithful to follow these new "dogmas". That is for ME and anyone else to condemn!
4. Does attending an "una cuм" Mass lead to compromise with the devil? That would be speculation and opinion. But even if it did, it's not for Fr. Cekada to bind the Faithful to one of his opinions, as if it were Catholic dogma. That is just not an option.
One cannot commit sin that good may come of it. THAT is a non-negotiable Catholic moral principle.And yes, it's sinful for a priest to presume to excommunicate other Catholics, cleric and lay, and to forbid attendance at other "competing" Masses.
Fr. Cekada was a mere priest operating (under supplied jurisdiction, I might add) during a Crisis in the Church. It was not his place to usurp the role of Pope. Or to bind the consciences of his Faithful in matters of opinion. That is over-stepping both Catholic morality AND his authority as priest.
One of the risks/tendencies/fruits of sedevacantism? Maybe I shouldn't say that out loud, as it might start a sede vs. non-sede debate...