Does this therefore support shunning? How could I answer someone who says it does?
Back then allowing someone into your house had social implications that are different than modern society. The word Greek used in 2 John 1:10 oikia denotes a household, not just a dwelling, but the dwelling of a family. A Christian family head was supposed to turn away false teachers, not shun them, just turn them away. The landscape of the early church was that of mass confusion. Something great had happened and many political and religious ideologies scrambled to cover it up or provide adequate replacement. This created an army of miscellaneous false teachers. The best way to deal with these cockroaches was to not allow them into your "house" as teachers. I don't think shunning was really the practice here as the early Christians were supposed to maintain diplomatic relations with all neigboring ideologies. They were supposed to follow in the footsteps of their Master and die for their enemies. Without good relations with neighboring ideologies the speading of the good news would be hindered. It would be reasonable to disallow the teaching of a contrary doctrine within your house. To allow such would denote weakness of leadership. Nonetheless, what you allowed into your house was considered what you deemed to be acceptable. This was a social norm of the day and nothing out of the ordinary.
Notice the Greek word didaché which is translated "teaching" in most translations of 2 John 1:10.
teaching, doctrine, what is taught.
So, if someone identified themselves as a teacher of what you as the head of a Christian house considered heresy you would not allow them in your house as a teacher. This doesn't mean that they are not welcome as a guest in your Christian house, but not as an instructor. This ideology is along the lines of freedom of religion. A house has to the right to turn away a false teacher, just as we today have the right to turn away the Jehovah's Witnesses out in the field ministry. Remarkably even today we have the same problem that they did back then. We have to keep them out of our houses as teachers. Which would mean taking them into your house as a Bible teacher would not be appropriate because they clearly teach false things. To be their friend however would not be forbidden, only warned against.
The early christian church would have looked a lot like a cult.
They died for their faith and each other in horrible fashion. Their sacrifice will never be forgotten or whitewashed by the likes of you.
-Sab