Mat 20:20  Then the mother of the sons of Zebedee came to him with her sons, and kneeling down she asked him for a favor.
Mat 20:21  He said to her, "What do you want?" She replied, "Permit these two sons of mine to sit, one at your right hand and one at your left, in your kingdom."
Mat 20:22  Jesus answered, "You don’t know what you are asking! Are you able to drink the cup I am about to drink?" They said to him, "We are able."
Mat 20:23  He told them, "You will drink my cup, but to sit at my right and at my left is not mine to give. Rather, it is for those for whom it has been prepared by my Father."
Mat 20:24  Now when the other ten heard this, they were angry with the two brothers.
Mat 20:25  But Jesus called them and said, "You know that the rulers of the Gentiles lord it over them, and those in high positions use their authority over them.
Mat 20:26  It must not be this way among you! Instead whoever wants to be great among you must be your servant,
Mat 20:27  and whoever wants to be first among you must be your slave —
Mat 20:28  just as the Son of Man did not come to be served but to serve, and to give his life as a ransom for many."

Curiously absent from John Bevere’s "Under Cover" is any mention of Jesus’ own words about leadership.  Verse 25 taken directly and literally unravels the covering argument.  The covering proponents try to redefine "Lord it over" and "user their authority over" to be much more extreme than they really are.  In doing they attempt to make the case that there is a more moderate biblical way of exercising authority and an illegitimate abusive form of exercising authority.  The text here makes no distinction.  When Jesus referred to "rulers of the Gentiles" the disciples could very well have been thinking of the Roman Centurion in Mat 8.  The Gentile rulers the Jews would have been familiar with would have been the commanders of the Roman army.

The Roman army had a command and control structure with rank and authority.  Jesus told the disciples that they weren’t supposed to be like that.  Why?  Because they were called to be servants.

The servant leader. Jesus chose a servant as the countermodel for His followers. Nothing could be farther from our idea of greatness or leadership. We tend to see, as did the disciples, the pomp of power. The TV cameras focus on the great seal of the United States, a hushed quiet falls, the band in the background plays “Hail to the Chief,” and the announcer’s voice is heard: “Ladies and gentlemen, the President of the United States.” We feel that is greatness. That is what being a leader is all about.
But then Jesus directs our attention to a quiet person standing off camera; a person in overalls with the working tools of his trade. And Jesus says that is greatness! That is what being a leader is all about.
This graphic contrast must have jolted the disciples just as it jolts us. Yet Jesus clearly wants us to see each of these people as leaders. Each of them is to be seen as having authority and the power to move other men. What, then, are the significant contrasts between the two?
While the secular ruler is above those he leads, Jesus said, “Not so with you” (v. 26). Instead of relational distance, there is relational closeness. The Christian leader must seek to be one with those he or she is called to serve.
Instead of “exercising authority” as a ruler who demands and enforces conformity, the Christian leader is to abandon coercion. Jesus said firmly and plainly, “Not so with you.” Force, manipulation, demand—all are ruled out in the way by which the servant leader exercises Christian authority. Outward force can produce conformity, but it can never produce that inner commitment which moves people to choose to follow Jesus.
How, then, does the servant lead? By serving! The secular ruler speaks the commands, but the spiritual leader demonstrates by his example the kingdom way of life into which he is called to lead others.
No wonder Peter picked up this same theme and wrote as an elder to fellow elders, “Be shepherds of God’s flock that is under your care … not lording it over those entrusted to you, but being examples to the flock” (1 Peter 5:2–3). By serving, the Christian leader demonstrates the greatness of the love of God, and gently motivates others to follow him. “Whoever wants to be first must be your slave—just as the Son of man did not come to be served, but to serve, and to give His life as a ransom for many” (Matt. 20:27–28). (Richards)

Lord it over

Young’s literal translation renders one section "exercise Lordship" rather than "Lord it over."  The word is katakurieuo and it merely means to master or bring under power.

Exercise authority over

The word translated "user their authority over" is katexousiazo and it means just how it is translated: to exercise authority over.

Jesus’ disciples would have been familiar with how leadership worked in the Roman empire and how it worked in their own communities.  Jesus addresses this as well in Mat 23.

Does this mean we have no leaders?  No.  God gifts people with the ability to lead and we should have cooperative and open heart to hear what God might say through them.  That doesn’t mean we shouldn’t be discerning in what we hear, nor should it crowd out our direct connection with God.  The role of leaders is not to make us dependant on them, but to help us reach maturity in our direct relationship with God.

Eph 4:15  But practicing the truth in love, we will in all things grow up into Christ, who is the head.
Eph 4:16  From him the whole body grows, fitted and held together through every supporting ligament. As each one does its part, the body grows in love.

Leaders help us establish God’s rule in our lives, not replace it with their authority.  Sometimes our leaders do speak God’s words, but it would be dangerous and arrogant to assume that people can speak for God all the time merely on the basis of their position.  This is why we need a vigorous and equipped church to discern.

Leaders gain (and lose) the authority to speak in to our lives by the criteria Paul appealed to his letter in 2Corinthians.  He appealed to things such as the changed lives of the Corinthians, his sufferings, his honest exposition of scripture and his devotion to the pure gospel.  See the rest of the list here.  He didn’t appeal to rank or position.

If our leaders turn to underhanded methods, false teaching, or exploiting people they lose the right to speak in to our lives.  At that point scripture provides instruction on how to address the situation (Mat 18:15-17, 1Tim 5:19-20).  We are not to accept any abuse of power.  Paul admonished the Corinthians for letting the super apostles take advantage of them (2Cor 11:20).

Richards, L., & Richards, L. O. (1987). The teacher’s commentary (576). Wheaton, Ill.: Victor Books.