I was inspired to write this in reaction to reading Catherynne Valente's recent unfortunate article on Steampunk -- to which I presently decline to link. The specific exchange arises from her defense of her comment that if something calls itself steampunk she is entirely justified in assuming it will suck, because 90% of it does.
I can already hear the groans of any surviving First or Second Fandom who actually read my e-scribblings.
Let me now take everyone back in time, courtesy of James Gunn
, to the 1953 WorldCon, at which the great Theodore Sturgeon spoke about the poor quality of Science Fiction criticism:"When people talk about the mystery novel ...they mention The Maltese Falcon and The Big Sleep. When they talk about the western, they say there's The Way West and Shane. But when they talk about science fiction, they call it 'that Buck Rogers stuff,' and they say 'ninety percent of science fiction is crud.' Well, they're right. Ninety percent of science fiction is crud. But then ninety percent of everything is crud, and it's the ten percent that isn't crud that is important. and the ten percent of science fiction that isn't crud is as good as or better than anything being written anywhere."
Most people now refer to "Ninety percent of everything is crud" as "Sturgeon's Law," though he called it "Sturgeon's Revelation." In 1958, he expounded on it further:I repeat Sturgeon’s Revelation, which was wrung out of me after twenty years of wearying defense of science fiction against attacks of people who used the worst examples of the field for ammunition, and whose conclusion was that ninety percent of SF is crud.
Using the same standards that categorize 90% of science fiction as trash, crud, or crap, it can be argued that 90% of film, literature, consumer goods, etc. are crap. In other words, the claim (or fact) that 90% of science fiction is crap is ultimately uninformative, because science fiction conforms to the same trends of quality as all other artforms.
Magazine, March 1958
I imagine the fact that SFF authors are saying "ninety percent of X is crap" to dismiss a subgenre of SFF has Mr. Sturgeon turning in his grave. Happily, he illustrated the bankruptcy of the critique and gave the proper rebuke: it's the other ten percent that matters.
 Stronger language did occur to me, but I will defer using to such time as I'm willing to devote the time and energy necessary to unpacking them.