I can sit back and appreciate this transformation since I was too young to notice when it happened to vampires.
You remember, "Dracula" and "Nosferatu" became "louis de point du lac" and "angel, the vampire with a soul".
We began bestowing upon them the very human gift of guilt. They began to regret their vicious bloodstained past and desire change which immediately cancels out any crimes they've committed, right?
If I were an optimist I'd say this cultural habit of embracing monsters speaks for the inherent compassion of the human collective. But I actually think it just says that we realize that evil can go far beyond the realm of bodily harm and zombies, bad as they are, are not capable of the breadth and variety of depravity that we humans are capable of.
That's why we've decided to forgive them. We realize we could do a lot worse than they can.
We are no longer afraid of the monsters. we accept that we are the monsters.