The Reformers sometimes, actually fairly regularly, used colourful language to describe their theological opponents. Take Calvin's sermons on Ephesians. The papists were not simply wrong in their doctrine they were "puffed up like swollen toads."
But think of how the New Testament typically describes false teachers:
They are wolves, blind guides, white washed tombs, dogs, uprooted trees, schemers, beasts, blots and blemishes, springs without water, pigs that have returned to the mud, dogs eating their own vomit, slaves, wild waves, and wandering stars.
Well you get the point from that sample don't you?
When we are told that false teaching is wrong the assertion is typically coupled with an image. And the image has a deeper effect on the imagination than a factual statement alone would make. This is the rule, it seems, and not the exception in the New Testament. Nevertheless it is a point that is so repeatedly made that we may well have missed the wood for the trees. It has been there all along, but not always being attentive and observant bible readers we may well have failed to notice something that has been literally staring us in the face.
There is something in this association of error with particular vivid imagery that alleviates the false dichotomy of the head vs. heart that plagues (now that is an image for you) evangelical thinking. The apostles do not present false doctrine as if it were comparable to mathematical error. By using appropriate images they make clear that false doctrine is disease ridden, grotesque, and diabolical. And they do so by appealing to the imagination.