Question:
I understand that Protestantism is heretical and/or contain heresies. And that todays Protestant is not a formal heretic, but are fallen away Catholics who now follow Protestant teachings, and claim to be Protestant formal heretics?
Answer:
Your question does not admit of a categorical answer because various individuals are involved and thus their respective culpability in leaving the Church will likely vary. Leaving the Catholic for Protestantism is certainly grave matter, but grave matter is only one component of a mortal sin. To be a formal heretic you have to be subjectively guilty of mortal sin. Which means you also have to had made your decision to leave the Church with full knowledge and complete consent of your will (CCC 1859; see 1854-64).
Let us pray for all fallen-away Catholics, realizing they’re not beyond God’s mercy (see CCC 846-48).
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