This excerpt is from Cult-Proofing Your Kids, chapter 6, by Dr. Paul Martin, founder of Wellspring Retreat. Here he distinguishes between theologically heretical churches, Christian fringe groups, and what he terms 'totalistic, aberrant, Christian organizations' (T.A.C.Os). Having met and counseled a number of former members of the Geftakys Assembly, he includes the Assembly in the 'TACO' category.
These are groups or churches which claim to be based on the Bible, in whole or in part, and yet deny or distort core doctrines of the Bible such as salvation by faith in Christ alone apart from legalistic works, the Trinity, the deity of Christ, the inspiration and authority of the Bible, the person and deity of the Holy Spirit, etc.--doctrines which the Christian Church throughout its history has consistently affirmed. Each group in this category denies the first or second doctrine mentioned, and usually one or more of the others. Some also employ mind control techniques to recruit and keep members. Examples: the Mormons and the Jehovah's Witnesses; the "local church" of Witness Lee has been grouped in this category, but has been successful in court in fighting this allegation.
In a very general sense, the religious groups in this classification identify with the dominant religious traditions of North American, and therefore, according to a theological definition, are not strictly cults. Although all claim to be biblically based and Christian, many deviate (in terms of social practice or doctrine or both) from what is conventionally understood to be traditional conservative Protestant evangelicalism. Membership in one of these groups does not necessarily preclude one from being a Christian in the truly biblical sense. These groups are sect-like fringe movements on the margins of mainstream Christianity. Examples: the "prosperity" Word of Faith movement.
Churches and groups in this category hold to the fundamental doctrines of true biblical faith, and yet their concepts of church leadership/authority and discipleship are unbiblically strong and authoritarian. Leaders commonly expect or require members to seek their advice and counsel (and often permission) on virtually every decision in their lives, including marriage, dating (if allowed at all), employment, place of residence, education, roommates, home and car purchases, etc., etc. These groups demand and expect a high degree of spirituality of their members, and this entails a rigidity of lifestyle that leaves little room for personal expression or individual focus on spiritual gifts or natural talents if these do not fit in with the program of the church. There is usually a very strong emphasis in the church on evangelism and discipleship with the expectation that everyone will participate with the same zeal and in the same way. These are high-demand authoritarian groups. Examples are Christian Growth Ministries, the International Church of Christ (as distinct from the mainline Church of Christ) and the Geftakys Assembly.
Further reading about cultic groups and sects: