Just to make it clear: “The Nine” weren’t dismissed from the SSPX because of the sedevacantist position. This is attested to by the fact that Father Collins did not hold the position until much after he left.

Actually it was Bp. Guerard Des Lauriers who invented anti una cuм position iirc

Any evidence to support this rather monumental claim?

Schism means "cutting". It's where we get the word scissors, right? Anyone who takes a scissors to Christ's Mystical Body, mercilessly lopping off chunks here and there -- that is a schismatic. Whether the target is the Pope or some other group of Catholics. Either way, the schismatic SEPARATES HIMSELF from the Mystical Body of Christ.

Right, some home-aloners would fall into this category (sedes are the only catholics in the world, and I don't live near a sede chapel (why don't you move?), so I miss mass for long periods of time).  Avoiding valid sspx masses for reasons they created in their head.  
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Or, it's arguable that the "una cuм" issue is potentially schismatic, if followed to the extreme, where one missed mass on sundays.
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What if a Pope embraced a new religion (I don't know, let's call it "Conciliarism" or "Modernism") while rejecting true Catholicism. Wouldn't he be the schismatic one?

Fr Hesse argued that the entire V2 system is schismatic.  They reject Eternal Infallible Rome, but accept current fallible new-rome.  I would agree.
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Nevertheless, the EXACT SAME THING applies to the dogmatic R&R (we have a couple here on CI), those who denounce sedevacantists as non-Catholics and heretics.

Yep.

Are the sedevacantists the Schismatics, I think not!

You out there with the forked tongue — Continue to defend your pope, the representative of Jesus, who is, God.  Remember the Trinity!  You defend him by calling him POPE!

Hey Stubborn!  Obey God rather than man? look here what you man is doing!   Say good bye to the Mass of all times, say hello to your MESS!

You obviously don't even know what you're saying, you're not mocking me, you're mocking the Church's highest principle.

Myrna, very simply, a Principle is something that is always universally applicable, it's absolutely integral and fundamental to all things, the more important the matter, the stronger we rely on our principles because all things of any importance flow with principals. Principals are always first and always present before everything else. When we say: "you stand on your principals" - it simply means you're basing right and wrong and your actions on those things that are always most important above, beyond and before everything else.  

The Church's highest principle means as our first duty, we are bound to always do what is right no matter who wants us to do wrong.

It is with very good reason St. Paul said: "Let him be anathema." So, let him be anathema. And pray for him, that's the only thing we can do about it and praying for him is the duty of every Catholic.

Stubborn I didn't create that video, your hero did.  It is getting more and more obvious that you are on his side.

Your words on the above post have no meaning except to make your ilk feel comfortable, thinking you must know what you're talking about.

He is your hero, not mine, you're the one who posts so much about him, not me, you must be on his side, I'm not.

And I was hoping the Church's highest principle did mean something to you. Myself, I learned it as a little kid from my parents, sometimes with a belt, but I learned it alright. I did not know then however, that it was the Church's highest principle. I'm a bit surprised your nuns neglected to teach it to you as a child.

Highest principle the Pontiff,

   No, the highest principle is Divine Truth (from Christ), or as you like to say “Divine Law”, which is another term for doctrine.  The pope, like all humans, either goes along with doctrine or not.  The Church, as guardian of doctrine/Divine Truth, continues on, whether the pope errs or not. 
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The Church, a Divine institution, continues IN SPITE OF a bad pope.  His personal loss of faith does not change doctrine. 

Yes, you are correct. However who determines what divine truth is? Without any doubt, in Catholic ecclesiology, it is the Vicar of Christ.

I think not. With the exception of a very, very few, the pope does not even speak to basically anyone for nearly his entire reign, except only very rarely.

Reminds me of this snip from Who Shall Ascend?

"....So, what is so burdensome about all this? Who, it might be asked, has an easier assignment? Everything has been instituted with incomparable wisdom. After almost two thousand years, the Church has developed into an organization of excellent structure. The doctrine is certain; the moral code is incontrovertible in the main; the divine liturgy has been (had been) refined to a perfection; the code of laws worked. In a word, the spiritual doctrine, the tradition, the authority, the experience, the customs, the supernatural objectives all have been established. With a little prudence and a little caution on the part of the pope, Holy Church will practically run itself!"