Since you are aware of Auctorem Fidei, you should definitely know that heretics use ambiguity to disguise heresy
Of course, but truly ambiguous statements, which could be either true or false depending on how one wishes to interpret them, cannot be objectively teaching error. And that’s all that infallibility does, isn’t it? Prevent that from happening?
Take religious freedom: it is true that man has a right to religious freedom and to be free from being forced to act against his conscience, or prevented from acting according to it, privately or publicly, in religious matters - within due limits!
Why? Because as the Church has always taught, true freedom consists in doing God’s will, and the right to religious freedom can be nothing other than the First Commandment itself. Everyone has the right to freely worship the Holy Trinity in spirit and in truth, and Catholics in particular. Similarly, nobody should infringe upon this, or acts in good conscience, within due limits - where infringing upon those who have a badly formed conscience may well be understood to be just such a limit. There is nothing in the text of Dignitatis Humanae that would condemn, say, the Albigensian Crusade or Catholic Integralism and a confessional state - but even in the Middle Ages, Jєωs, e.g., were allowed their private worship. So why doesn’t the docuмent state these things as such? Because that was probably not the intention of those who drafted it - but that doesn’t concern infallibility, which is not inspiration to teach truth but prevention from teaching error. The whole thing should be thoroughly amended or just consigned to the flames, buts it’s failings - it’s the conciliar equivalent of the Godfather 3 following Trent and Vatican I -
do not necessarily imply promulgation of heresy.
The heresies which are taught today on the basis of Vatican II we’re doing the rounds “in” the Church long before that council and would in all likelihood be “mainstream” even without it, just like the liturgical abuses and destruction of the mass were just further enabled by the Novus Ordo, but were sneaking in anyway.