The Presbyter John in the Epistles is not talking of people who go against what Jesus himself taught, but those who deny that Jesus was in any way human, there were a lot of Docetic Christians around, even in the Congregations John writes to.
"For many deceivers are entered into the world, who confess not that Jesus Christ is come in the flesh." This establishes that, from the time the Epistle was first written, there were those who had Docetic Christologies, believing that the apparently human person of Jesus was actually pure spirit or not even come at all !
Now, teaching THAT Docetic view of the Christ is ALL that the Epistles of John could justify a person being D.F'd for, without reading in to the Scriptures what is NOT there, a favourite trick of JW Org.
I doubt anyone has ever been D.F'd from the Org. for teaching that !