Discipline can take many forms. One is to exclude from the congregation a person who no longer wants to live by God's standards, or who refuses to do so. A person who is disciplined may repent and turn around. In the process, the congregation are also disciplined in that they learn the importance of conforming to God's high standards as outlined in scripture.
Does this mean that if a Christian stumbles into sin they are automatically expelled?
Disfellowshipping someone should be used only after attempts of reasoning with that person have failed, then the congregation is justified in expelling them from their midst.
Paul told the congregation:
Disfellowshipping is a demonstration of love for the wrong doer, it encourages them to repent.
Disfellowshipping someone because they do not believe the same way would be wrong, it is for those that are sinning, breaking God's law based on real scripture!
Everyone understands according to their own spiritual growth. Instead it is to be used for those that are in a clear state of sin according to Gods word (example: fornication, covetous, breaking the ten commandments), and not the organizations view of sin (example: wearing jewelry, dancing), but then again, would it make any sense to fellowship with this type of organization anyway?