I certainly can't account for all the hardcore fans, but articles I have read, many complaints are from the non-readers of the book who are voicing their problems with it, whereas those who have read it (I haven't) are not shocked at all that Dany is a murdering wackadoo psycho.
We all have our own perspective of the description 'hardcore fan.' I see a fan or casual follower as someone who simply watched and admired a movie or show and nothing more. A hardcore fan dives into every media aspect of that movie or show or book.
Much like the Alien/Predator hardcore fans here. I would be surprised any frequently active member here has never explored beyond the 12 movies this forum is based on. Many of the members here have explored way, way more details on the characters, locales, plot, etc. than what the films present.
And from what I have read, it's not like Dany's M.O. is some obscure info buried in a fanboy's blog on his
freehosting.com site. Her M.O. is shared in great detail by the creator himself in the novel.
So when it comes to it, if those disgruntled viewers don't really know Dany's real M.O., then that hardly qualifies them as "hardcore fans."...... imo