I don't know whether you are aware but to call SV'ism a novelty is ignorance of history.
I have pointed out quite a while ago, and so have many others, not sure if you have read it or not. If you have not, well that is fine, but here it is so that you can stop claiming such ignorance.
St. Vincent Ferrer "deposed" anti-Pope Benedict XIII for the simple fact of wanting to refuse to resign for the good of the Church. He did it in front of religious superiors, Cardinals that were appointed by the one he thought was the true Pope. St. Vincent was a prodigy genius, plus a man who was gifted with prophecy, miracles and great holiness. He was already a professor of Logic at the early age of 20's. He came about this after a serious study of tradition, months of fasting and prayer. It was then and ONLY then that he was able to do such a thing once he verified the magisterial teaching of the Church on the topic.
We have had approx. 40 something anti-Popes (not including the modern anti Popes) depending on which historian you talk to, most of them agree on all the ones with a few disputed cases. So to think that it is "a novelty" is completely dishonest at best, and plain bad will at worse. This is especially true if you have been on the internet forums for quite a bit. You can't claim that sort of ignorance that a newcomer might be able to claim who knows nothing of the faith.
Instead of making claims, no matter how long it takes you. Go and read ANY book pre-vatican II on the history of the papacy. It is precisely history which is on our side, and to make the BOLD claim that SV'ist are twisting somehow St. Robert Bellarmine shows simply how ignorant you are on the matter at hand.
St. Robert Bellarmine CLEARLY teaches that a heretical pope loses his office, St. Thomas Aquinas is in the same boat if you examine his treatises on heresy, St. Vincent clearly had the same position (if you don't believe me then actually go read his books), . Quit being intellectually lazy and actually read the material you are discussing about, instead of getting brainwashed by arguments which have already been refuted. When I went and did the reading myself, I found to my amazement that it was the SV'ist who were right. It also best fits the current crisis of the Church and the root of the problem.
The vatican II sect represents the false bride of Christ, the anti-Church. There is a long line of anti-Popes, before the final culmination of the Man of Sin, a.k.a. THE Anti-Christ. This has been the commentary of many great Saints with respect to who will the anti-Christ be? And how he will take the reigns of power, how he will be able to deceive the elect. The only man who fits the perfect description is an anti-Pope, this is why in the original D-R commentary it said this, St. Bernard says this and many other Doctors + theologians (Card. Manning says the same). It is not far-fetched, it is not "novelty" as you seem to think. It is only a novelty to those who are too stupid to read what tradition has actually said on the modern crisis. No instead you want to rely, on your emotions, and put what you conceive as God's "mercy" in a box of your own doing. Ohh if SV'ism were true, "the gates of Hell have prevailed against her" and such intellectual gobbledygook that is constantly uttered as theological arguments. Or the famous, your good Dad and bad Dad argument.
Go ahead and attend the Novus Ordo or the masses of those false priest who have been ordained in the New Rites. At the end of the day, when you die you will see that we were right from abstaining from them. Instead of disdaining the opinion of men whom the Church has actually called as authorities on these matters, you defer to your own emotions as proof. St. Bellarmine was called as Master of Controversies (he was the head of that department in the College of Rome), the same goes with St. Francis de Sales, he was known as the Master of Controversies. St. Antoninus another famous Doctor, St. Cyprian and I can keep going on all day.
No instead you cling to a few men who can't even make a coherent arguments on the topic, who would turn over their graves if they saw the position of the SSPX on the matter. The SSPX claims to be the champion of Cajetan and the 4 other theologians who are in the minority on this point. Yet, Cajetan, Suarez and company don't even agree with each other + their position is not even the same as that of the SSPX. So go ahead and keep telling yourself that everything makes sense under the SSPX theological framework. Its okay if the Church gives you demons to worship such as Wojtyla and Roncalli. Intellectually its no problem for you, because the Church as you understand it can give you poison. BUT no my dear friends, the Church is the Bride of Christ which is protected by Infallibility. Keep telling yourself that a whore can somehow with its idolatry and ecumenism, be able to somehow be at the same time the True Church of Christ. But as for me and my SV'ist brothers we want to keep our sanity and logic in check. Non possumus, that simple.
Yes it is spiritually detrimental at this point which position you really hold. Does it make you a heretic, ipso facto. No, not necessarily but it really depends on the individual cases. If the individual defends in their mind intellectually that which is apostasy as licit, then they incur the same anathema's that the Vatican II sect has incurred, but if they resist these heresies intellectually then they keep the faith, but there are still consequences to holding these men who dress in white as true Popes. It will make all the difference who you go to confession to, where you go to mass, what laws you follow for fasting etc... Whether or not you go to actual Sunday mass or Saturday mass (Jewish worship as opposed to the concept of Catholic Sabbath worship a.k.a. Sunday).
Please do study the issues, it makes a huge difference when everyone is in the same page. Actual beneficial discussion can take place when everyone has done their reading and homework.