The most merciful thing in the world, I think, is the inability of the human mind to correlate all its contents. We live on a placid island of ignorance in the midst of black seas of infinity, and it was not meant that we should voyage far. The sciences, each straining in its own direction, have hitherto harmed us little; but some day the piecing together of dissociated knowledge will open up such terrifying vistas of reality, and of our frightful position therein, that we shall either go mad from the revelation or flee from the deadly light into the peace and safety of a new dark age.
-H.P. Lovecraft
I don’t think I understand the problem. You say that “consequentialism is a slam-dunk as far as practical rationality goes,” this comment is interpreted as the claim that “The moral theory called Consequentialism is true,” and the person you’re talking to asks you what you think about some common and relevant objections to that moral theory.
What’s gone wrong? “Consequentialism” is used in philosophy as a term for the view that the morality of an action depends only on the consequences of that action. So I don’t think you can blame your interlocutor for interpreting the term this way and raising relevant objections to this view. You seem to be using the term in an idiosyncratic way—as referring to the view that we should think about the consequences of our actions before performing them (or something like that).
The lesson of your story seems not to be that we should avoid using terms like “consequentialism,” but that we should be careful to explain exactly what we mean by a term if we’re going to be using it in an idiosyncratic way.