Xanthippe & Peony
That scripture is talking about those that deny Jesus came in the flesh or do not keep to his teachings.
JWs who disassociate themselves normally do so for the reason that they no longer go along with Watchtower's false teachings. Most still have a strong faith in Jesus and his teachings. At baptism these days you have to agree to work along with the org, and if you no longer wish to do that, they will say you have disassociated yourself. However there is nothing in the scriptures that says if you reject any false teachings you should be shunned, and certainly nothing in the bible that says you have to go along with anyone teaching something that is not scriptural.