What if the doctrine proves to be wrong? Is it still heresy? surely truth is more important?
Can you explain what - ministry of active rebuttal of the fallen angels. Tell them that there’s no proof of the devil means - and where would I find a copy of their proof
Clearly you - like me some years ago - have a very unclear grasp of the meaning of being a disciple of Christ. One of the basic tenets is: Christ does not lie, nor does Scripture. When they speak of Satan as a living spiritual being, they don’t mean a metaphor. When they say: “For we do not wrestle against flesh and blood, but against the rulers, against the authorities, against the cosmic powers over the world of darkness, against the spirits of wickedness in the high places.” When Christ says: “I saw Satan fall from the sky like lightning” or “Here comes the prince of this world, he has no authority over me.” But I understand that in your situation the Sacred Scripture is perhaps simply “scripture” and not proof of anything.
Truth is the single most important thing.
Christ said: “I am the Truth”. He also told His Church: “I will be with you until the end of time”, and He told His apostles and their successors: “those who hear you hear me, those who reject you reject me”. Of course - in matters of
faith and
morals. On these, the Church teachings do not err. The world, in 20 centuries, has seen all sorts of societies arbitrarily establishing and imposing what was right and wrong, good and bad, lawful and illegal. Emperors have fought the teachings of the Church and legitimately elected representatives have opposed them. But the Church has not backed of one step on the timeless truths she has been entrusted with by God - regardless of what societies or other religions or even schismatic groups have said or done.
Now let’s be a bit more specific. The “doctrine”, so to speak, is subdivided into different levels. Teachings called
de fide are
known to be right. Examples include the Holy Trinity, The Real Presence of Christ in the Eucharist, etc. At the bottom of the list we have
sententia probabilis, which are theological opinions that are probable (f.ex. the opinion of whether or not Our Lady died before the Assumption). Non-infallible teachings, while not requiring the assent of faith, cannot be disputed nor rejected publicly, simply because the benefit of the doubt must be given to those possessing the fullness of teaching authority.
I can explain, of course, what I meant. I refer to bishops and priest involved with the rite of exorcism, as well as the lay faithful that collaborate with them to some degree - including psychologists and psychiatrists. These people know very well the reality of the fallen angels lead by Satan. And there are plenty of writings on these topics for you to study, in fact it is a field called demonology. Also, just to mention a few recent, well-known books written by exorcists: “Interview with an exorcist” by Fr. Jose Antonio Fortea; “The Rite” by Matt Baglio (about Fr. Gary Thomas, on which a movie was loosely based); “Exorcism and the Church Militant” by Rev. Thomas J. Euteneuer; “Exorcist, A Spiritual Journey” by Fr. Jose Francisco Syquia; “Evidence of Satan In The Modern World” by Rev. Leon Cristiani.
If you want “proof” such as a video or live evidence etc., you are simply not in a position to have access to such material, and it should be more than enough for you to be taught that this reality exists and that there are people who directly confront it - besides, of course, the spiritual warfare that each devout faithful wages every day indirectly.
But to forget that ultimately the devil is responsible for our fallen nature, and that he does actually tempt us, that’s a huge mistake. Remember what St. Peter wrote in the New Testament 
Yes, what I meant is that a Catholic must give the assent of reason to the existence of the devil. To resist this revealed truth is in fact a sin of heresy, which is not inevitable at all 