Complex sentence: Gibson believes that the Second Vatican Council introduced explicitly heretical and forbidden doctrines into the Catholic Church in order to destroy it from within, and he holds that every pope elected since John XXIII, inclusively, has been an anti-pope or illegitimate claimant to the papacy.
Split into simpler sentences: Gibson believes that the Second Vatican Council introduced explicitly heretical and forbidden doctrines into the Catholic Church in order to destroy it from within. He also holds that every pope elected since John XXIII, inclusively, has been an anti-pope or illegitimate claimant to the papacy.