The purpose of the Church is to disciple others to follow Christ and to obey everything that He commands. Obedience to Christ, then, is critical to the life of the Body, and our gatherings together should be one of the primary places we learn how to follow Christ together on a daily basis.
Guarding your Family
Sometimes there are predators who come into your church family and you need to have discernment to recognize them and move quickly to remove them. This might involve meeeting with them in person to let them know why you're asking them to leave, or you might need to pull them aside and give them a warning if you think they just need a friendly reminder to change their behaviors.
The kinds of behaviors we need to be wary of are those who cause division or strife in the Body: