Your definition of fascination is insufficient. I am fascinated by Hitler for instance, but I find him to be repulsive, evil and there are zero traits of his that I desire. What fascinates me about him is how someone could be so different from the "norm", how someone as evil as him came to power, maintained it and so forth. There is no glorification there, there is no desire and there are no valuable traits of his that I can identify. I am also fascinated by the Zodiac Killer, but mostly I am fascinated with the totality of the case, not him specifically. If I knew who he was, I probably would be somewhat bored by him.
Glorification would have to also include some sort of outright praise for the person or the person's actions. Name a serial killer (it's serial, not cereal for Christ's sake. How can I take you seriously when you swing and miss on the spelling that bad?) whose actions have been outright praised. Name any killer who receives genuine praise from the masses. I suppose Che Guevara might fit the bill, but I could argue against that as well; I think a lot of people don't realize how many people's deaths he was responsible for. But that's neither here nor there.
My point is that fascination, even obsession, does not entail glorification.