This is a plausible theory I've got-- I don't know if formal work has been done in the area.

I used to read discussions of the definition of science fiction until I came to the conclusion that there was no point. People have strongly felt intuitions about what science fiction really is, and seem to have no way of knowing that everyone doesn't agree until they bump up against other people's definitions.

But why would one have a strong attachment to a definition of science fiction?

I suggest that people invent such definitions from a few early, emotionally charged experiences.

I still find it hard to believe that Delany and Zelazny really wrote http://en.wikipedia.org/wiki/New_Wave_science_fiction