It's been a while since I read the book, but it makes sense to me people failed to identify with the doctor as the bad guy at the end of the movie.
In the book, we're shown what amounts to a small love story between him and a vampire, and the living-vampires brutalizing the dead-vampires, and finally the doctor.
There's a ton of build up to the reversal that the alt ending does not seem to have.
