I've come to notice a common pattern in church history, in the teaching of error.
In the initial stage, when the teaching is introduced, it is taught as an improvement open the traditional, orthodox view. The traditional and orthodox openly reject is as erroneous.
But later on, it is introduced as if it were the traditional, orthodox view - or equivalent to it. Instead of contrasting it with the truth, it pretends to be the same thing, more or less. It re-appropriates orthodox terminology, with a heretical meaning. It uses the old words, but gives them a new, altered, reduced meaning.
For example, the heart of the Christian gospel is that Christ died for our sins - which means that his sacrificial offering was penal (his death was on account of an offence, that of sin) substitutionary (it was not a penalty for his own sins - but for ours). Liberalism, however, re-appropriated the language. Re-appropriating language so that it is being used ambiguously by different speakers tends to empty it of meaning. So now "Christ died for our sins" simply means that his death benefits us in some, as-yet-to-be-defined way. When liberals define it, the words "Christ died for our sins" means the same as a view which one of the orthodox could quite happily mean by the phrase "Christ did not die for our sins".
Similarly with the deity of Christ. To make ourselves precise and clear when choosing terms, we can no longer say "the divinity of Christ", because liberalism - whilst pretending to be orthodox, or orthodox enough to avoid being excommunicated before it had got sufficient power within the institutions - reduced the meaning of "divinity" to mean just "like God in some as-yet-to-be-defined way". After defining it, you knew that when a liberal said "Christ is divine" the actual content could be reduced to "Christ is not divine".
But what about closer to home? Liberals threw off their pretences of taking the Bible seriously generations ago. Now that they have got their power bases, they no longer hide what they mean. Where's the real action today amongst those seeking to subvert the historic teaching of evangelical churches?
Within the camp, one major battle is that for the Biblical doctrine of creation. Historically, the Christian church has confessed that God made the world out of nothing in the space of six days, as an immediate act of his power through his spoken word. The world was very good, but the sin of the first man Adam brought about a cosmic fall. But in the hands of many evangelical leaders today, the doctrine of creation is simply that God is the one who made creation, without specifying anything more.
And as they describe their doctrine of creation, its content turns out to be the same as what the orthodox meant if they were to describe one of the main options previously available under the heading "God did not create the world", namely, evolution. When the new evangelical leaders say "I believe in a historic Adam", then once you unpack what he means, you find that it was previously listed by historic Christianity under the possible meanings of "I do not believe in a historic Adam". "I believe in the Fall" means the same as "I do not believe in the Fall" and "Genesis is a historical record" can be further explained as "Genesis is not a historical record".
We've seen how well this worked out with liberalism. It destroyed churches from within, just as Peter said it would: "there will be false teachers among you, who will secretly bring in destructive heresies" (2 Peter 1:1). Evolutionary teaching is destructive of the foundation of the Christian doctrine of creation, which is in turn the foundation of the coherence of the gospel of Jesus Christ. It's no use pointing out that some of these teachers are nice people, and that their creeds are otherwise orthodox enough. Once you allow termites to start chewing up the basement whilst you avoid going down there to do battle with them, you have in principle accepted the destruction of your house. That is so whether you or they rejoice in that outcome or not.