**They aren’t heretics, they simply (from the Catholic point of view) hold erroneous views. **
But once they know the truth and still choose to disobey Christ, aren’t they heretics?
That he is the truth, the light and the way? That no one gets to heaven except through him? (Not Mary, not the Saints and not the Pope)
Yep, the heretics would not agree with him.
Vatican II and the Catechism put it this way: "Basing itself on Scripture and Tradition, the Council teaches that the Church, a pilgrim now on earth, is necessary for salvation: the one Christ is the mediator and the way of salvation; he is present to us in his body which is the Church. He himself explicitly asserted the necessity of faith and Baptism, and thereby affirmed at the same time the necessity of the Church which men enter through Baptism as through a door. Hence they could not be saved who, knowing that the Catholic Church was founded as necessary by God through Christ, would refuse either to enter it or to remain in it."