Have you ever noticed how much we depend on labels when dealing with differing viewpoints, and how much those labels tend to take on a life of their own? In many cases, we may choose to describe our own position with a label which we see as completely positive and to which no-one could conceivably object. Yet before we know it, that label comes to represent something very different than we intended.
For example, who could object to the term "egalitarian"? It means someone who believes in, favors, and works toward "equality." An egalitarian is one who seeks fairness, who pursues justice for all, and who works toward the common good. Implicit in those ideals are a deep humility and selflessness.
I am sure that those who first used the term "egalitarian" in the context of a debate about gender roles within Christian marriages and Christian churches did so because they thought it sounded relatively innocuous. They wanted to avoid the negative baggage often associated with the "feminist" label and emphasize that their position was more moderate and more positive.
Similarly, those who coined the term "complementarian" were seeking a label which would be entirely positive and which they couldn't imagine anyone objecting to. After all, "complementary" means "to complete and bring to perfection," "to combine in such a way as to emphasize each other's qualities," to be in a state of harmony and mutual fulfillment. The term was no doubt chosen to disassociate from positions of male domination, on the one hand, while emphasizing that the sexes are nevertheless distinct.
Yet as much as we try to come up with innocuous labels to which no one should object, in the process of debate those labels tend to take on more polarized meanings. To many egalitarians, "complementarianism" is merely a whitewashed term for "patriarchy" and "male superiority." To many complementarians, "egalitarianism" is largely synonymous with more radical forms of "feminism." Consequently, each side ends up feeling as if their views are being misrepresented and distorted. Conversely, each side sees the other as representing a slippery slope toward a more nefarious extreme.
So while I think it is helpful to define terms and identify what we mean by the labels we use, it is even more important that we not use those labels as a way to cram our theological opponents into a box, refusing to listen to them carefully because we think we already know where they are coming from. In any theological debate, we must be careful not to devote ourselves to the promotion or demolition of an "-ism." Rather, our goal must always be to develop and communicate a clearer understanding of what the Bible teaches.