Christ’s prescription when a professing believer offends us is straightforward.  Confront him/her privately. (Mt 18:15) If that fails to restore fellowship then  involve one or two others to [a] ensure there’s no misunderstanding, and [b] discretely encourage resolution. (Mt 18:16) Failing here,  take it to court: tell the church. Her verdict is considered binding and final; those who refuse it are treated as outsiders, unbelievers. (Mt 18:16) This is ultimate spiritual authority.
Personal offenses being the most common and critical challenge to unity, Christ is actually telling us how to handle any type of corruption among professing believers; whether it be a divisive spirit promoting destructive teachings or blatant sin, this pattern is evidently applicable.
So who or what is this church, the final authority deciding all spiritual matters impacting the well-being of the body of Christ? (Col 1:24)
The word church is from the Greek ekklesia, meaning assembly or congregation (1Co 11:18), and the fact that all are subject to its judgement implies unity. In other words, spiritual authority lies only in a unified brotherhood; without this, the church is lifeless and powerless, nothing more than decor in a broken world.
To destroy a brotherhood, and thus the church herself, impose any type of hierarchical leadership; elevate a small group to exercise spiritual authority over others. This undermines the foundation and subverts the purpose of the assembly. It’s the default model in our churches today, and the result is easily observed: spiritual devastation.
Promoting this destruction presumes that Christ uses “ekklesia” symbolically here, that He must be refering to leaders representing the assembly. Yet, being honest with the text, we must still expect the brotherhood to be informed and unified, or such leadership could not intelligently speak on its behalf.
To maintain integrity in light of Christ’s instruction, we must acknowledge the centrality and spiritual authority of a unified brotherhood. This is what Christ is building, nothing less, the strongest force on Earth. (Mt 16:18)