People who do not acknowledge God are cut off from the church because the whole point of the church is God, and because the things related to God that are called theological teachings give the church its structure. Therefore to deny the existence of God is to deny everything having to do with the church. The denial itself is what cuts them off; that is, they cut themselves off. God does not cut them off.
They are damned as well because those who are cut off from the church are also cut off from heaven. The church on earth and the angelic heaven act as a unit, just like the inner and outer self, and like the spiritual part and the physical part in each of us. God created us in such a way that our inner self is in the spiritual world and our outer self is in the physical world.
Therefore to make us permanent and everlasting beings, God made us citizens of both worlds so that the spiritual part of us, which belongs in heaven, could be planted in the physical part belonging to this world the way a seed is planted in the ground.
from True Christianity, Volume 1, Page 19