All human communities practice shunning in some form. Society imprisons criminals for example. If a group is very specific, such as an "Iphone rules" meetup group, and one guy starts showing up talking about how great Samsung is and how everyone should switch.....he may not be welcome in the group.
But a structured communal shunning program based on private meetings and proceedures hidden from view, presided over by three or more men, and meant to extend to everyone that associates with that group worldwide......is not even close to the type of "shunning" done by early Christians even as a best guess.
the idea that someone thinking and feeling different than you, is not add odds whith normal Christianity. The individual groups make a decision on who to not support based on the persons behavior. It is not a decision handed down to them, that they must then in turn obey under threat of being ostracized themselves. there is no support for such a thing, even in vague principle.