If the OP was an indult Catholic or something I could see this argument... I mean it wouldn't be particularly rigorous or convincing to an SV but at least it would be internally consistent on its own merits
By contrast, this guy is an SSPX Resistance guy. I really dislike, and consider erroneous, the kind of papal absolutism that leads most people to Sedevacantism, but let's be honest, the SSPX Resistance effectively, for all intents and purposes, has no pope. The "normal" SSPX is already minimalist on papal authority (though I'm not convinced they're wrong to be so), they want to be normalized by Rome but only under certain conditions. But even this is not satisfying to the Resistance guys here.
SSPX Resistance is just as fringe a position as Sedes. Even normal SSPXers aren't reacting to this pontificate the way, the rest of the world does.
Now, fair, you could say, well I accepted Obama as the President, but I accept him as a BAD President, not as a good one. And I accept Francis as a BAD pope, but still, in fact, the pope. The "birthers"/Sedevacantists deny that Obama/Francis is really President/Pope at all.
My problem with this is, accepting Obama as a BAD President is analogous to being an FSSPer. Being normal SSPX is analogous to engaging in civil disobedience. But being SSPX Resistance... I don't know, the best analogy I can think of is in essence saying the President has no right to do anything, maybe even try to overthrow him, but still insist that he IS the President, and, in this case, bash the Birthers who say he's not President.
And then pretend as though this is somehow mainstream. No different than attending the local Catholic next door.
To be honest, even though I'm a Sedeplenist, and Eastern Rite for that matter, I still wouldn't make THIS argument against the Sedevacantists. I think they're wrong because I think they're making a judgment call they have no right to make, but not because a lot of people disagree with them. Like... who cares?