Sojourner, you're wrong, it's not simplistic at all, precisely because all words carry certain implied meanings. My whole point is that the implied meanings and values that one generation or culture reads into a word may be totally different from the beliefs and values of an earlier culture, and that's why it can be misleading and wrong to apply a modern term to something from the past, something whose underlying meanings are totally different from what that term implies. The point is that it's misguided and ethnocentric to assume that your perceptions and experiences can correctly and without modification describe the intentions and goals of people decades or centuries in the past. I'm not talking about universals like "green," but about culture- and period-specific designators like the name of a political, social, ideological, or literary movement. These terms do not exist in a vacuum, but come with a lot of unspoken baggage attached, and so the user must be aware that one's own assumptions are not necessarily the same as those of the historical figures one is speaking about.
And Kegg, yes, you have a point. As I've acknowledged repeatedly, such labels can be useful conveniences, as long as you use them advisedly and be aware that they may be approximations or oversimplifications. They can work, but there's also the risk that they can be hugely misleading, so care should be taken.
I guess it depends on whether you're using the word "steampunk" to refer to a specific literary movement or more broadly as a particular type of story. My critique was based in the fact that the term was coined to refer to a specific movement of the '90s and '00s, so it would be a mistake to say that earlier works are part of that same movement; at most, they are antecedents or ancestors of it. However, I grant that the term has acquired a broader meaning through association, in reference to a particular style or subject matter.