Many post-Newtonian physicists believed that physical reality consisted of just matter in motion in absolute space. For them, physicalism meant reducing everything to particle interactions. The only nodes in the fundamental causal graph were properties of particles. However, it gradually became clear that reducing all physical phenomena to this basis was a very difficult, if not insurmountable, task. But by introducing a new element into the fundamental physical ontology -- fields -- one could in fact formulate much better physical theories.

Now consider a hypothetical early physicalist resisting the introduction of these new nodes into the fundamental causal graph. He might have objected to simply introducing a new primitive object into the ontology on the grounds that this object is "mysterious" or "magical". The correct response would have been, "Why is my primitive any more mysterious or magical than yours?" If introducing a new primitive allows us to construct more and better explanations, it might be worth it. Of course, the new nodes in the graph need to be doing some work, they need to be allowing for the construction of better theories and all that. You can object to them on the grounds that they do not do that work, but simply objecting to them on the grounds that they are new irreducible nodes isn't much of an argument.

My impression is that property dualists like Chalmers think of irreducible psychological properties and laws along these lines. They are new irreducible nodes in the causal graph, yes, but they are essential for constructing good explanations. Without these "psycho-physical" laws, we don't have any good explanations of the phenomenal quality of conscious experience. Maybe the dualists are wrong about this, but they are not (at least not necessarily) simply positing an idle dangler that does no explanatory work. They are claiming we need to add new nodes to our fundamental causal graph, and that these nodes will do important explanatory work. Also, the nodes are linked to the pre-existing nodes by law-like relationships (hence the term "psycho-physical law"), just as the new "field" nodes were linked to the pre-existing "particle" nodes by law-like relationships. If we have predictable, empirically discoverable laws connecting these nodes, I don't know why one would describe it as "mysterious" or "magic". Dualists of this stripe aren't simply helping themselves to a semantic stopsign, they're writing a promissory note. They are saying that incorporating psychological (or, perhaps more plausibly, broadly informational) properties into our fundamental ontology will lead to better theories.

All that said, I AM NOT A DUALIST. I just don't think the rejection of dualism is virtually a priori true, that there is no non-magical alternative to reductionism. I think there is a substantive empirical disagreement about what our best theories of consciousness will look like. This is not a question that can be settled by simply defining one position to be true, by declaring that "consciousness" is just a label for a set of neural interactions. If that is what one means by "consciousness", then the dualist position doesn't even make sense. And if your definition of a word renders your opponents (some of whom are quite smart) incoherent, then chances are you are talking past them rather than genuinely refuting their position.