By rabid (and this applies to all types of fandom) I mean those that practically froth at the mouth when someone suggests that an author's books are less than perfect, or that another book might be better, or that something in the story just didn't make sense. They throw tantrums when movies don't include their pet scene or get a detail wrong. I think the truly rabid ones have entwined themselves in their 'fan' identity so deeply that any criticism or suggested imperfection becomes a personal attack.
Of course, on the site I posted this on, there are many very young, very rabid fans. Perhaps in time they'll realize that there is more to read than that particular author.