I have heard this argument so many times that I cannot count from sedevacantists and I think it is a good argument for sedevacantism. But he acts as if this argument ends all debate and proves that sedevacantism is true. I disagree. He does not adress the point which I think is a strong agrument for sedeplenism which is that it is a teaching of the Church that if the whole Church accepts a man as Pope it is proof that he is really the Pope. All of the concilar Popes (especially John XXIII and Paul VI. There were a few thousand sedevacantists who rejected the conciliar Popes I believe starting around the time the Novus Ordo came out but I don't think that there were enough for it to be significant) have been accepted by the whole Church so that should prove that they were and are true Popes. Even today of the billion people who claim to be Catholic all but a few thousand sedevacantists accept Francis, so pretty much the whole Church accepts him.
This is illogical as it would make a valid papacy subjective, dependent on what the people think. Our Lord did not set up a democracy. This is different then when you have two Catholics who claim to be Pope and one is accepted by the vast majority. That is not what makes a man pope. Unless you can show me where it is taught that you can "pope" a public heretic in this manner?