e. St Bellarmine does NOT mean that we can "treat them as heretic" by kicking them out of office without due process. This contradicts every legal foundation ever created.
f. In the case of Luther, he would've been suspended immediately for his 100 thesis and he would've lost any "spiritual" authority from that moment. But...his office/temporal authority (and his membership in the church) did not cease until AFTER an investigation/correction.
g. As St Paul teaches, those in error should be corrected twice, then afterwards, cast out.
h. The problem with many sedes is they fail to distinguish between spiritual penalities for heresy (which many times only God knows) and the process for determining temporal penalties. An investigation is necessary, by an authority, before any temporal penalties can exist. Or it's just an opinion. No layman can kick anyone out of office for any reason.
This is why Pope St Piux X and XII changed the conclave laws. They knew that canon law outlines multiple spiritual penalities for heresy, which kick in immediately. They also knew that orthodox cardinals/bishops were far outnumbered and that Modernists held positions of power. Which means that the legal structure necessary to investigate/"clean house"/change the Modernists with heresy was impotent. Which means that these evil men would still retain temporal control of offices, per canon law, even if they were closeted (or even open) heretics. Because the Church is a visible organization which functions like a govt for temporal matters.
So they, knowing the future was dire, made the decision to keep the VISIBLE/Temporal structure of the Church intact (i.e. allow material heretics to vote) even if this means that a) spiritually speaking, the Church would be papally sedevacant for a long time (until God intervened), and probably 95% cardinal/bishop sedevacant globally
b) temporally speaking, the Church would be "ruled" by modernist heretics.
Not only is this situation the practical reality, but it's also the only temporal solution to the problem. Neither St Pius X nor XII could stop the infiltration; it had already happened (it's arguable that Pius XII was a cooperator, so he must be deemed an fellow infiltrator). St Pius X couldn't convert these heretics. And I don't think "cleaning house" is an effective solution either, because (in St Pius X's day) a) it had never been done, b) it would've caused total chaos, c) most modernists would've claimed to have been orthodox, so how do you prove heresy when the "deep church" (which was very active in the early 1900s) would effectively subvert your every move? I don't think people realize how infiltrated the Church was, in St Pius X's time. He often complained to his assistant of being "alone" (he meant, orthodox-wise).
So, the only solution is to prepare for the future situation that we are living in today. Where 99% of the Church is either a material heretic or mostly pernicious infiltrators. But how do you separate the two? How do you determine a) the cowardly unorthodox from b) the pernicious evildoers? Even if you knew, how do you replace them when the "deep church" is against you?
Similar to the Arian heresy, when 95% of the church hierarchy were heretics. The church still functioned temporally. But they all eventually re-converted and returned to orthodoxy. There was no mass "kicking heretics from office" and replacing them with orthodox bishops/cardinals. That didn't happen, nor is it a practical reality. Did they abjure their heresy before the church returned to normal? Absolutely. Did these heretic clergymen suffer spiritual penalties and lose spiritual authority? Sure, St Athanasius' life proves this. But did they also STILL KEEP their offices during a chaotic, unprecedented crisis? Yes.
The only solution is to "keep the Church going" from a temporal standpoint (i.e. keep the visible structure operating) even if spiritually speaking, it's been hallowed out by an enemy. And wait for God to resurrect His Bride, as only He can do.