Unfortunately material heretics (even public ones) exist inside the Church of Christ.
I think this attitude is grounded in the Americanist heresy first condemned by, I think, Pope Leo XIII. It's essentially an extension of the idea of "religious liberty".
The concept of religious liberty is more than simply the idea that everyone may accept or reject any particular religion. This is not really a doctrine but is simply a fact. All men may indeed reject the Truth; this is a fact that is due to Original Sin. But the idea of religious liberty is much more than that.
According to the heretical understanding of religious liberty which is, I think, the chief heresy of the Conciliar sect, all men have a fundamental right (which, by definition, is accorded by God Himself) to worship or not to worship Him according to any personally understood concept of God and of religion. The root of this heretical belief is in, what Pope St. Pius X called, vital immanence, in which the very understanding of God is derived, not from Divine Revelation, but from the interior sense of God which God Himself manifested in many ways through many cultures and societies.
Thus, the Church is not viewed as a Divinely instituted and perfect organization united by one Faith but is a mere human institution united simply by a president, i.e., the pope. It is in this
heretical understanding of the Church that even manifest and pertinacious heretics can be members of the Church
in good standing as long as they, individually, claim to be members of the Church.
What's even more disconcerting is the fact that the Conciliarists expand this to allow that even people who, individually, specifically deny membership in the Catholic Church or even who specifically deny any Christian faith, may still be members in some way of the Catholic Church and therefore be saved. I don't think they even claim that they have an "imperfect union" with the Church anymore.