I'd argue that its value in its heyday worked socially, not intellectually: it was used in the formative months of ILX as a way to blank or short-circuit arguments, not to develop them. The word was useful as part of the culture emerging in ILX, viz.

1. We have started a music board in which we are talking seriously and hopefully intelligently about music which a lot of people dismiss, putting it on equal or better footing with what they don't dismiss.

2. If a lot of the dismissers joined the board it would most likely lose the character it was developing, because it's quite small and there's a lot of them out there.

3. If we have a word that dismisses the dismissers then it will work as a filter on the numbers of them coming in. The fact we can't agree on EXACTLY what it means is, AT THIS STAGE IN THE COMMUNITY, less important than its existence and the fact that we generally agree on the badness of the arguments it dismisses.

4. Oh bollocks the word has taken on a massive life of its own and has become a total rod for our own backs.

This is all huge post facto rationalisation in that nobody thought through "rockism" working like this, but I think it's how it *did* work.