You’re right that it’s wrong, but ostracism doesn’t strike me as something that can be outlawed—not just because it’s one of our fundamental primitive social behaviors, but because of logistics. I’m curious how you envision it working? That is, you could probably forbid a church from declaring excommunication in a formal fashion, but could you actually stop its members from shunning someone? It would raise a lot more questions, like what if one member of the church is revealed to have abused another? Does the church still have to welcome them back?
It sounds like your group wouldn’t readily welcome a member who wasn’t an intelligent, rational individual. I wonder, if a current member experienced a crisis that led them to a kind of blind, irrational faith, would they still be equally welcome?