as a little bit of leaven leavens the entire bread, meaning if you allow such a person to co-exist in the assembly of God, he will also cause the entire assembly to also lose their salvation.
You got that part right, but that is the easy part. The rest not so much. This is your big belief:
1Co 5:5
turn this man over to Satan for the destruction of his body, so that his spirit may be saved on the Day of the Lord.
So, how are they going to turn him over to Satan? Convene a witches coven and conjure him up? Have a midnite Satanic Mass? But you ignore the rest of the verse:
so that his spirit may be saved on the Day of the Lord. But if his body is destroyed by Satan how will his spirit be saved?..Through his repentance. Being turned over to Satan is to remove him from the church. In reality all outside the church belong to Satan. He has removed himself spiritually already, now he has to be removed phsyically so he understands the consequences of what he has done; he is removed from the church. 1Co 5:13 God will judge outsiders. "Expel that wicked man." But his spirit may still be saved....how?....through repentance, grace, forgiveness which is what he and we live under. We don't know if he repents and is allowed back in; that part of the story is not given to us. But the hope is given to us.
1Co 5:1 It is actually reported that sexual immorality exists among you, and of a kind that is not found even among the gentiles. A man is actually living with his father's wife!
1Co 5:2 And you are being arrogant instead of being filled with grief and seeing to it that the man who did this is removed from among you.
1Co 5:3 Even though I am away from you physically, I am with you in spirit. I have already passed judgment on the man who did this, as though I were present with you.
1Co 5:4 In the name of our Lord Jesus, when you are gathered together (and I am there in spirit), and the power of our Lord Jesus is there, too,
1Co 5:5 turn this man over to Satan for the destruction of his body, so that his spirit may be saved on the Day of the Lord.
1Co 5:6 Your boasting is not good. You know that a little yeast leavens the whole batch of dough, don't you?
1Co 5:7 Get rid of the old yeast so that you may be a new batch of dough, since you are to be free from yeast. For the Messiah, our Passover, has been sacrificed.
1Co 5:8 So let's keep celebrating the festival, neither with old yeast nor with yeast that is evil and wicked, but with yeast-free bread that is both sincere and true.
1Co 5:9 I wrote to you in my letter to stop associating with people who are sexually immoral—
1Co 5:10 not at all meaning the people of this world who are immoral, greedy, robbers, or idolaters. In that case you would have to leave this world.
1Co 5:11 But now I am writing to you to stop associating with any so-called brother if he is sexually immoral, greedy, an idolater, a slanderer, a drunk, or a robber. You must even stop eating with someone like that.
1Co 5:12 After all, is it my business to judge outsiders? You are to judge those who are in the community, aren't you?
1Co 5:13 God will judge outsiders. "Expel that wicked man."