I used to occasionally remark that consequentialism is a slam-dunk as far as practical every-day rationality goes; if you care about what happens, you think about what will happen as a result of possible actions. Duh.

The predictable consequence of this sort of statement is that someone starts going off about hospitals and terrorists ?and organs and moral philosophy and consent and rights and so on. This may be controversial, but I would say that causing this tangent constitutes a failure to communicate the point. Instead of prompting someone to think, you invoked some irrelevant philosophical cruft. The discussion is now about Consequentialism, the Capitalized Moral Theory, instead of the simple idea of thinking through consequences as an everyday heuristic.

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.