If you're going to further discuss the faithful&discreet slave, have him look closely at the scripture (Matt 24:45-51).
Where does the Bible even insinuate that these few verses are anything more than one simple parable, surrounded by many other parables?
Where does it imply that the slave in this parable represents a group of men in the 20th century?
If the vast majority of Christ's true followers (great crowd) would have to be under the submission and education of this small handful of men at the most crucial time in history, wouldn't Jehovah have given us more than one simple parable in a few verses to tell us this? I would think if the everlasting life of millions of people depended on submitting to the f&ds, it would be spelled out pretty clearly for us.
Also notice that the parable doesn't say there was a faithful slave. It mentions one slave, and gives an example of what would happen if the slave acted wisely, and what would happen if the slave acted foolishly.
In light of the many times Jesus tells us to come to him for life, where is the scriptural basis for adding another layer of management and insisting that no one can come to Jehovah except through them?
Good luck with your brother! I doubt anything you can throw at him will make him leave the org, but if you can make him think, it may be the first step.
Keep us posted . . .