Here are what I thought were a few good and clear facts from the article. From my original post..and it's not bashing..it's telling the truth.
The legalistic Adventist sects, such as Jehovah's Witnesses, Seventh Day Adventists, Christadelphians and the old-style Worldwide Church of God may vary in actual doctrine and teaching, but they have massive areas in common.
When William Miller sought to refocus Christianity away from, the previously accepted focus on Christ's atoning work on the Cross, to a new focus on the envisaged Second coming and on Bible prophecy (especially that found in Daniel and Revelation); he was drawing on strands which were in no way new, they had been attempted before in the Old World, but had not been able to prosper because of the wide accessibility of a more deeply Biblically grounded theology. The New World, however, was determined to be 'open' religiously, this certainly came to assist the new, exciting Adventist worldview, providing, and environment in which it could flourish.
All the Adventist-type cults and sects, as an American phenomenon, can be traced back to the 'groundwork' of Miller.
It matters not whether we speak of Joseph Smith, Ellen White, Hiram Edson, Joseph Bates or Charles Taze Russell (who became the first leader of the Watchtower Society - later Jehovah's Witnesses --in 1896.) Herbert W. Armstrong was very much of this theological lineage in all of his influences.
Miller, like almost every sect/cult founding Adventists who would follow him, had little deep knowledge of the Word of God and had not been a long-term practising Christian. He had never studied Greek or Hebrew and it is known that he only used the Bible and Crudens concordance in his work. All the founding Adventists followed a 'Me-only' approach in which they believed that God was revealing new truth - only to them! They even rejected the new understandings of other Adventists. In short, their approach became notable for their sublime sense of self-sufficiency! These men and women who have never been masters, of even one of the biblical languages in which the inspired texts were originally written, were never prepared to check their conclusions against the more time-honoured conclusions of men such as Luther, Calvin, Augustine. In this sense, it has been easy for Adventists, since they have never felt the need to defend their teachings against the more thoroughly biblically-grounded; and in Adventism itself, typically, the people are held in subjection to various charismatic leaders and do not dare pose questions. Further, most such sects have painted a picture (also very much part of Adventism) that they alone have all truth and that those who hold other biblical views are the tool of Satan!
David Koresh, of Waco, Texas fame, was also an Adventist, originally of the Seventh Day Adventist sect, later leaving to pursue his own highly idiosyncratic theological path.
We need to consider this question of Justification, since mainstream Christianity upholds Justification by Faith alone, while no Adventist cult/sect can wholly go along with this. Why? Because if one is finally justified, or made right with God, because of holding to the sufficiency of the Gospel - as traditionally presented - then why the need for Adventism with its morass of additional teachings? In some ways, it really is as simple as this. Of course, some Adventist groups do carefully attempt to uphold the bone fide Christian position in their publications, but as every former Adventist knows this is not the way it is for those within the group. The teaching is usually that, yes, Christ died for us, but it is not enough just to believe this, one also has to... and here the legalism is introduced.
Under the New Covenant, Man is 'made right' with God, in other words justified, by accepting Christ - there are no other grounds! The Adventist cults and sects do not fully appreciate, nor understand, what occurred upon the Cross....
The moment any Adventist sect founder comes up with their version of the gospel, usually requiring adherence to the import of their own writing and conceptions, the plot is lost! Paul has already illustrated that the Gospel doesn't need supporting with extra philosophies (Ephesians and Colossians), nor with any partial adherence to the Old Covenant (Galatians and Romans), believers in Christ were not to attempt to put 'New wine into old bottles' (Luke 5), the Old Covenant is now, for Christians , obsolete (Hebrews 8:13)
So does this mean that all the established Protestantor Baptist churches have got it right? Concerning their perception of the Gospel, yes. But they have occasionally taken on some dreadful influences. The rationalistic God - denying liberal theology of the last century, for instance, has taken a terrible toll and has been a destroyer of churches. But good conservative evangelical theology has fought back very well producing a plethora of biblically sound writers and theologians, especially in the UK. Names such as C.S. Lewis, John Stott, Alister McGrath and Martyn Lloyd-Jones spring to mind.