Richard Oliver
I would say personally say that the person chose to disassociate or formally remove themselves as a witness. I would indicate that Paul said not to even eat with a man that was once called your brother. I would also indicate that Jesus stopped his association with Judas when he excused him from the lord's evening meal before his betrayal of the Christ.
That's, what he really said:
(1 Corinthians 5:911) 11 But now I am writing YOU to quit mixing in company with anyone called a brother that is a fornicator or a greedy person or an idolater or a reviler or a drunkard or an extortioner, not even eating with such a man.Nothing about a lovely person - leaving the religion. Not one word.
And nothing about the word "once" (once called your brother. Paul speaks of the present here - not of the past).