We can't totally blame the witnesses for there stance. The practice of shunning is found in the Bible.
Robo Bobo
"anyone who claims to be a brother or sister" - this is not talking about someone formerly baptized who decides they want nothing to do with the religion
I don't think that thought is in line with what this Scripture says. It clearly is an admonition to stop mixing in company with anyone who was Formerly a brother but who now chooses to live another life.