You should not be greatly surprised to learn that orthodox biblical doctrine (orthodox refers to the accepted norm) is the primary means through which doctrinal error enters the body of Christ. In this day and age, however, it is probably news to some and a needed reminder to many.
In Peter’s second letter he makes a statement of fact identifying this. He writes (2 Peter 2:1b NIV):
They will secretly introduce destructive heresies, even denying the sovereign Lord who bought them—bringing swift destruction on themselves.
The word for secret, here, is (παρεισάγω) pareisagó which means to place something along side of something else (in order to hide it). Get the picture? It is behind the façade of orthodoxy that false teaching is introduced. The erring Teacher depends on orthodoxy in order to introduce his (or her, unfortunately to the many in the body of Christ asleep at the wheel who have embraced the ordination of women or women acting enrolls reserved for those ordained so they are not ordained they are, in fact, exercising those roles) parasitic philosophy. Often, the very ideas contained in the false teacher's novel but poisonous doctrine-which become absorbed and accepted without rigorous vetting-are later used by some to attempt to overthrow the very orthodoxy they claim to have believed when they made entry into the mainstream.
In Peter’s letter he describes these pseudodidaskalos (false teachers) as both heretics and apostates. An apostate is someone who once held to orthodox views but later, moved from those views and now espouses something contrary to orthodoxy. A heretic, on the other hand, is much broader and definition since it may include to somebody who at least on paper with their lips says they agree with orthodox fundamentals.
The word for heresies (αἵρεσις) refers to a mix of opinion and truth. That is, instead of Bible Teachers being bound by the text and disciplining their teaching so that they are not reading into the text, a foreign meaning, the heretic does just this and makes up sensational teachings based on reading a meaning into a text which, as Peter describes it, are “cleverly devised stories". So a heretic can continue to hold to orthodox views but introduce erring doctrines which corrupt the edifice of remaining doctrine and generally, at some point, will approach (usually in their ignorance but often simply in their arrogance) even their orthodox views, but not always. So what you have, in essence, is an orthodox heretic.
And this is one of the most critical points here. Within Christianity, but most specifically Protestant, Evangelical and Fundamental Christianity, the battle cry in defense of Teachers who have introduced teaching that has sorely injured God’s children is that “they are orthodox”. Well friend, Peter is trying to tell you something and you ought to listen. Someone uttering agreement with orthodoxy or even elaborating on it effectively at times does not immune them from teaching heresy nor does it warrant your deliberate ignorance and unwillingness to see their error for what it is. Peter tells us, it is through orthodoxy that these other teachings enter! If someone says they are orthodox my response is, "great, but now I am going to vet your teachings and if it contains error or heresy, sorry, but I will call it what it is" and you ought do so as well, reader.
Many people are afraid of the word heretic because of its misuse. But it is a biblical word. Be not afraid, believer, and use it effectively. But to the main concern here.
If you take a look at Benny Hinn’s website and read his statement of belief you will find that he is orthodox. He agrees with all the main doctrines which identify a person as a Christian in doctrine. Yet, Benny Hinn has introduced many erring concepts, in fact, some even challenging the very orthodoxy he claims to believe.
But take someone which others might claim is less egregious. John Piper calls himself a Reformed Baptist and not only has he made clear that he believes basic orthodoxy but he has defended some of its tenets. Yet, in his book Future Grace, Piper introduced a heresy which taught that our justification was not final the moment we receive Christ but depended upon our fidelity until death. This is heresy to the Protestant, Evangelical and Fundamentalist.
As well, Piper’s book, Desiring God: Meditations of a Christian Hedonist, is based on a heretical premise. Piper declares quite clearly the following (bold mine):
“I found in myself an overwhelming longing to be happy, a tremendously powerful impulse to seek pleasure, yet at every point of moral decision I said to myself that this impulse should have no influence ... Then I was converted to Christian Hedonism. In a matter of weeks I came to see that it is unbiblical and arrogant to try to worship God for any other reason than the pleasure to be had in Him” (Desiring God, Introduction).
Notice what Piper heretically asserts, “that it is unbiblical and arrogant to try to worship God for any other reason that the pleasure to be had in Him”. This is not merely a statement without implications. It attacks the very nature of our relationship with God. In fact, it mocks the large and detailed biblical landscape which covers many facts of our walk with God and all of its properties. In another day and time, John Piper would have been made to either recant this assertion or rightly be labeled as heretic, regardless of his claims toward orthodoxy because again, simply being orthodox does not exempt one from being a heretic.
This is not a particularly sophisticated piece and it need not be. Rather, it is a reminder that many, today, are being pushed forward as accepted Teachers based on a faulty threshold which is orthodoxy. Simply because one claims to hold to orthodoxy does not exempt him from being identified as a heretic.
Obviously not all error is heretical. That is, someone may have exegetical misunderstandings which produce error but this does not come from a mix of opinion and truth, rather a flawed attempt at proper exegesis. So, not all error is of the heretical kind but the kind of error that is running rampant and its proponents are being shielded from rightly being labeled heretics, is the kind of error that is aggressively being tolerated in the name of a misunderstanding of when and how to identify heresy and label its proponents heretics. Sadly it is being practiced by some rather significant Teachers who are modeling a form of categorical ignorance which is inviting injury to many.