Heresy is different doctrine.
It is different not in regard to peripheral matters, but at the very point of what is most important. Heresy is a different gospel.
Whatever words or phrases that it may use, which sound and look the same as the orthodox ones, this cannot compensate for the fact that the thing itself is another gospel. And this makes heresy, for all its similarities, no gospel at all. It carries a different meaning and value beneath the common currency of God's words.
Honesty, integrity and truthfulness, demand that this be pointed out. Heresy simply is different, even if it seeks to pass itself off as the same. Out of loyalty to the truth this must be shown to be the case. Heresy must be named.
It exists as something distinguishable from the biblical gospel. Failure to name it will not alter its nature, or its difference from the truth, or its effects.
As the Bible commentator B. H. Carroll put it:
"Definitive truth does not create heresy--it only exposes and corrects. Shut off the creed and the Christian world would fill up with heresy unsuspected and uncorrected, but none the less deadly."
Quotation from Robert Martin "The legitimacy and use of confessions", in Sam Waldron,
1689 Baptist Confession of Faith: A Modern Exposition, p. 16