Ray Ortland had two tweets on heresy that I thought were worth reposting, partly because I want to remember them.
"'Heresy' is a valid category because some ideas are so misguided they endanger the soul"
It is true that some Christians find 'heresy' in every error. Not all doctrinal errors are equally severe. But behind the charge of heresy should ultimately be the pastoral concern. True heresy has eternal consequences.
"Heresy matters not because it is the "wrong" answer but because it reveals a wrong relationship with God."
I think this last one is so important. So many people today assume that if we are concerned about heresy we have turned God into an academic exercise. That God is a set of propositions. They say that this undercuts the relational nature of God. Some even say things like we shouldn't fight over our doctrines but point people to God.
The problem is that this never acknowledges that when it comes to truly heretical issues people divided over an issue are actually two (or more) different gods.
Heresy is not about 'answering the test questions right'-- the issue of heresy vs. true doctrine is about a right relationship with the right God.
Of course, the tweets said this more succinctly.