The current GB did an about-turn on the concept of the "evil slave" a few years back. Where formerly it was believed it represented an apostate influence breaking away from the organisation, now they just say it is symbolic and was a warning of what might have happened to the FDS.
In case you find the below TLDR, I've underlined the key points.
In the book "God’s Kingdom of a Thousand Years Has Approached" from 1973, they wrote:
60. (a) Were individuals who act like “that evil slave” appointed as such by the Master? (b) What do all such individuals form in general?
60 If there is a class of spirit-begotten, anointed Christians who act according to the description of “that evil slave,” it is not the Lord Jesus who appointed them and put them in charge of his domestics or “household staff.” Individuals who were once members of the “faithful and discreet slave” class may break away for selfish reasons such as personal ambitions, power over others and self-indulgence. These self-seekers may form themselves into groups in pursuit of their goals. However, they would form one general class, separate and distinct from the “faithful and discreet” slave class.
61. What is it reasonable to say as to whether there would be cases that could be used to illustrate what Jesus said about the “evil slave”?
61 It is reasonable to believe that the Lord Jesus would not use an illustration without having some cases, or a general case, with which to furnish an example of what he meant, as far as conduct and the outcome thereof is concerned. This would illustrate, not that Jesus appointed “that evil slave” class or type of Christians, but that it really happens to unfaithful, unreliable, untrustworthy, indiscreet Christians during his invisible parousia or presence just as he described.
62. What instances of this were there, especially during World War I days, and how did this affect the “faithful and discreet slave” class?
62 There were instances of this in the ranks of the International Bible Students Association right after the death in 1916 C.E. of the editor of The Watch Tower and founder of the Watch Tower Bible and Tract Society. There were attempts on the part of some individuals to seize power and control contrary to the provisions of the Society’s Charter. There were disagreements as to who made up the Lord’s approved organization. The power-seeking ones and those dissatisfied with sincere efforts to conduct matters according to the legal Charter and Bible principles were frustrated. They indulged in considerable ‘beating of their fellow slaves’ in a verbal way in print and by word of mouth and in judicial court. They put themselves on the side of the “confirmed drunkards” of this world, spiritually speaking, especially during those days of World War I. All of this put the stability of the organization, which was then under increasing religious persecution, to a great test. It brought a great trial upon the “faithful and discreet slave” class.
However, in a WT in 2013, the Org 'clarified' this to explain that the "evil slave" is purely theoretical - no-one is really an "evil slave", it was simply a warning to the FDS that that is what they might become if they prove unfaithful, which of course according to themselves, they are not!
“IF EVER THAT EVIL SLAVE . . .”
Jesus has placed the weightiest of responsibilities on the faithful and discreet slave—namely, overseeing the domestics and giving out spiritual food at the proper time. Jesus knew that those with greater responsibility have greater accountability. (Luke 12:48) Hence, he concluded his illustration about the faithful and discreet slave with a powerful warning.
Jesus warned about an evil slave who concludes in his heart that the master is delaying and who starts to beat his fellow slaves. When the master arrives, said Jesus, he will punish that evil slave “with the greatest severity.”—Read Matthew 24:48-51.
Was Jesus foretelling that there would be an evil slave class in the last days? No. Granted, some individuals have manifested a spirit similar to that of the evil slave described by Jesus. We would call them apostates, whether they were of the anointed or of the “great crowd.” (Rev. 7:9) But such ones do not make up an evil slave class. Jesus did not say that he would appoint an evil slave. His words here are actually a warning directed to the faithful and discreet slave.
Notice that Jesus introduces the warning with the words “if ever.” One scholar says that in the Greek text, this passage “for all practical purposes is a hypothetical condition.” In effect, Jesus was saying: ‘If the faithful and discreet slave were ever to mistreat his fellow slaves in these ways, this is what the master will do when he arrives.’ (See also Luke 12:45.) However, the composite faithful and discreet slave has continued to keep on the watch and to provide nourishing spiritual food.
The anointed brothers who together serve as the faithful slave recognize that they are accountable to the Master for the way they care for his domestics. The heartfelt desire of these anointed brothers is to fulfill their responsibility loyally so that they might hear a “well done” from the Master when he finally arrives.
A suspiciously easy brush off to the warning Jesus gave, IMO. Personally, I think Jesus WAS warning that those claiming to be Christians taking the lead in the time of the end could fall into wicked practices and become effectively an "evil slave" - and that is indeed happening. There are too many repeated instances of the scriptures warning "keep on the watch", "keep testing yourself", "stay awake", etc, along with similar parables like the foolish virgins with no oil for their lamps, the wedding guest who is booted out for not being properly dressed, and so on, for it to simply be a light warning easily brushed off with "we're ok, we're eagerly listening to the voice of the Master", which is what the GB seems to say dismissively.
And of course, individuals and groups claiming to be Christian and taking the lead in many other denominations are also similarly proving false to Christ's commission. All such risk the wrath of the Master when he returns, so it's a very serious matter if one claims to be a Christian, especially if claiming to be in a leading and shepherding role.
Also, there are too many past examples in the Bible of leaders among God's people being 'corrupted' - from many prophets and kings in Israel, through some members of the early Christian congregation down to Judas - for individuals in Christian leadership roles to be overconfident about their position. From the Devil's point of view, such corruption is exactly what he wants, and from a human point of view, it has a certain inevitability as a tempting character flaw - as the saying goes: "Power corrupts..." etc.
