Firstly, the negative connotation is but the most recent way the word has been used to color something in an immoral or bad way. Even using the word cult in a secular way (“the cult-following of Twilight Zone”) seem to be older, and more positive overall.
Secondly, the word cult is a useful and suiting word in religious science when referring to religious worship and devotion - often aimed at a particular phenomenon within a larger religious context, such as a specific deity in a pantheon (in this light, the article use of the word seem less fitting).
Third, and I may be wrong on this one as I base it on pure intuition. From a Semitic perspective, other religious practices has been viewed historically as less legitimate, more primitive or outright as false practices at odds with say, Christianity. Those “heretic” practices has often been linked to Satan himself, causing many religious or spiritual traditions to be regarded as simply Satanic cults. Of course, this is negative press for the accused - but Satanism is also a Semitic religious idea.
My point is lost, but Should we continue to refer to Satanism as an immoral threat to society?