Too often "cult" is simply used because the religion isn't as old as the others (hello chr*stians, do you seen any irony in this???). Then there is the unfortunate fact that old religions tend to lose their "fizz" and become "respectable," dismissing once-held beliefs as "myths" while the so-called "cults" still truly believe.
I'm not sticking up for this particular group. I'm just saying that if you're going to erase the True/false dichotomy in religions the cult/non-cult one doesn't seem to make an awful lot of sense.
Cults are historically have been movements that seperate themselves from society/strong dominating leader and control/brain wash their members. Biblical Christianity has never had these traits. Mormomnism obviously began that way, though its memebers followed Jospeh Smith willingly. JW has some these characteristics but no one is being forced against their will as far as I know.