There were indeed charlatans in the Ancient World who perverted the meaning of the Gnostic path, to either appeal to those with narcissistic tendencies, or by charismatically using false lines of logic to create socially-manipulative moral confusion. In this way, these false prophets utilized an illusory veneer of the Gnostic intellectual approach to spirituality to find those among its milieu of monstrous ego, who craved validation for their secret hope of a hidden demi-divinity, or those of weak ego, whose poor self-esteem made them prone to exploitation, mistaking their submission for being spiritually valued. From the former type of victim, these charlatans obtained monetary contributions and political support, and from the latter type, offerings of heaping tithes, the running of dirty errands, and the giving of gross sexual favors.
So whereas good Gnostics preached that everyone had a spark of the Divine that could be nurtured both through selfless compassion, meditation and the acquisition of higher knowledge, gnostic poseurs preached an exclusive line, declaring that some people had only "animal souls" incapable of true enlightenment (and thus no preservation of identity in the afterlife), while others had "god-like" souls wrongly trapped in this world by demonic beings who sought to thwart their divine potential. And whereas good Gnostics preached that a healthy spiritual balance should (and could) be achieved between sexual/physical and spiritual/mental components of a person's being, gnostic poseurs preached counterintuitively that amoral, polymorphic, orgiastic sexual excess could lead to spiritual enlightenment.
This is not to say that charlatans have not used orthodox forms of religion for personal gain and immoral power. The historical record is full of conniving, cynical, avaricious, rapacious, lecherous, mendacious priests, popes, pastors and preachers of religiously honored cloth among every legally recognized sect and denomination. However, those who twisted otherwise enlightened Gnostic teaching (and thereby gave orthodox theologians the excuse to paint all heterodox sects with one broad taint of opprobrium) has parallels with our own time. The popular awakening in the mid-Twentieth Century to still imperfectly-understood Eastern forms of spirituality and discipline found itself being readily exploited by self-serving charlatans seeking to sponge off and enlist the support of middle class would-be hipsters and professional, media, and business people who fancied themselves the new aristocracy in the West of the Atomic and Computer Ages.
These were the first recognizable cults (in the popular sense of the term), which were sometimes quaintly odd (like the Space Brother movements of the '50s), to the more sophisticated perversions of Oriental teaching that resulted in underground communities where social alienation, cultural reprogramming, hypnogogic mind-control and prescriptive dietary malnourishment came into play under charismatic leaders, who themselves might be out-of-control narcissists, if not merely cunning sociopaths. These cult-leaders otherwise enforced their will through violent and psychologically intimidating bodyguards, if any of the members they had duped began to see through the mass delusion of their separatist community and sought to flee. It is doubtful that the false prophets of the Ancient World ever rose to the same level of total psychological control of their misled flocks with the near-perfect skill and sophistication that our modern-day examples have. Unfortunately, the false prophets are still among us in the 21st Century, both in orthodox and heterodox forms of purported religiosity, and using more pervasive forms of multi-media manipulation and legalistic intimidation to carve out and protect their paths of exploitation. In short, they are not so much "underground" anymore, but so obvious they have become largely invisible to the normally wary.
Yes, cults are alive and well, and less vulnerable to investigative reports by dauntless journalists. This is because today's cults are more powerful in their insidious consolidation and exercise of social-political control than the earlier forms that crept in during the first decades when the West was first throwing off the old fetters of oppressive Victorian restraint. Since then, so many have sought spiritual liberation and found themselves (after being promised the true light) caught in just a new web of bitter subjugation. That is why the good Gnostics were right: we must use our minds as well as our hearts to guide us through the thicket of deception and delusion.
There are predators (and packs of them) who prey upon every human need and desire, from the need to be loved, to the desire to feel important. This has been true from the beginning of civilization. Neither orthodoxy nor heterodoxy is a guarantee of trustworthy or morally respectable leadership. We must make the effort to be our own pilots of our souls, try to support what is recognizably good in others, but be on our guard against those who may misuse the spiritual mode to clandestinely do harm. We must each of us remember that we were all made in God's image, and therefore none of us deserves to be abused or made the slave of another. In a truly moral universe, love does not share the same space with submission to the egomania of another or an elite group of others. God loves all equally, and therefore all have equal access to God.