Okay, I found the relevant place in the video. It's a little after the 23-minute mark. The quote is as follows:
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Fr. Jenkins: There are some sedevacantists who are dogmatic sedevacantists. I don't even consider them to be traditional Catholics. There are some who will say "John Paul 2 was no pope. I can prove it. It's a matter of faith, and if you believe he was the pope you're not a Catholic." I don't even consider those people to be traditional Catholics at all, because they are usurping authority they don't have.
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This is madness. So the dogmatic sedevacantists are not traditional Catholics because they say people have to agree with them or they are not Catholic. But Fr. Jenkins does not consider them to be Catholic because they in turn do not agree with
his position of sedevacantism being an opinion.
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I'm not saying I'm a dogmatic sedevacantist, as I probably hold to the "opinion" version of sedevacantism the way he does. So before someone condemns me of doing what I accuse Fr. Jenkins of doing, which is what he in turn accuses the dogmatic sedes of doing, I hasten to say that I do not therefore consider Fr. Jenkins to be not a traditional Catholic. My point is just that his logic is an absurdity and that hoists himself on his own petard.
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Being too strong against dogmatism inevitably leads to ... more dogmatism.