Aren’t you misusing the term Apostate?

No, we are not misusing the term apostate. It is perfectly accurate to label Antipope John Paul II and his Bishops apostates. Pope Pius IX labels the “Old Catholics,” who merely denied Papal Infallibility (one dogma), as apostate priests in Graves ac diuturnae.

Pope Pius IX, Graves ac diuturnae (# 2), On the “Old Catholics”: “Having violently occupied parishes and churches with apostate priests, they have not neglected any deception or cunning to lead the children of the Catholic Church into wretched schism… Because it has always been the especially characteristic of heretics and schismatics to use lies and deception, these sons of darkness… [the ‘Old Catholics’] repeatedly state openly that they do not in the least reject the Catholic Church and its visible head but rather that they are zealous for the purity of Catholic doctrine… But in fact they refuse to acknowledge all the divine prerogatives of the vicar of Christ on earth and do not submit to His supreme Magisterium.”

In his book The Liturgical Year, Abbot Guérangerrefers to Martin Luther as an apostate:

“Luther would have the world believe Him (God) to be the direct author of sin and damnation… Calvin followed; he took up the blasphemous doctrines of the German apostate…” (Vol. 10, Feast of the Sacred Heart, p.428.)

In the absolutely strict sense used by canonists, the word apostate applies only to those who abandon all profession of the Christian faith entirely. In other senses, it is applied by Popes and Saints to heretics who give up the Christian Faith by virtue of their rejection of one or more dogmas; for, as Pope Leo XIII teaches, those who repudiate one article of the Faith reject in one act the whole of Christian teaching.

Pope Leo XIII, Satis Cognitum (# 9), June 29, 1896: “… can it be lawful for anyone to reject any one of those truths without by that very fact falling into heresy? – without separating himself from the Church? – without repudiating in one sweeping act the whole of Christian teaching? For such is the nature of faith that nothing can be more absurd than to accept some things and reject others. Faith, as the Church teaches, is that supernatural virtue by which… we believe what He has revealed to be true, not on account of the intrinsic truth perceived by the natural light of human reason [author: that is, not because it seems correct to us], but because of the authority of God Himself, the Revealer, who can neither deceive nor be deceived… But he who dissents even in one point from divinely revealed truth absolutely rejects all faith, since he thereby refuses to honor God as the supreme truth and the formal motive of faith.”

So Antipope John Paul II and his Bishops are certainly apostates, especially when we consider that many of their heresies involve not only a denial of one or more dogmas of the Faith, but a denial of the author of our Faith Himself, Our Lord Jesus Christ.