“If anyone comes to you and does not bring *this teaching, do not receive him into your house, and do not give him a greeting; for the one who gives him a greeting participates in his evil deeds (2John 1: 10, 11 NASB).”
 
The phrase “this teaching” refers to God the Son having taken on the type of sinless humanity that Adam had prior to the Fall (2 John 1: 8 NASB).
 “For many deceivers have gone out into the world, those who do not knowledge Jesus Christ (as God) as coming in the flesh. This is the deceiver and the antichrist (2John 1: 8 italics mine).
This type of humanity was necessary in order for God the Son to become the acceptable sacrifice in the capacity of the Lamb of God (John 1: 29 NASB).
This is what the b-e-l-i-e-v-i-n-g (placing one’s trust and confidence) in the PERSON of the Lord Jesus Christ is all about. To take the position that the Lord Jesus Christ was/is anything less than God in the flesh, is anti (against) Christ.
Believing in what He did in the flesh while on the cross to atone (pay) for the world’s sin debt (1Johnn 2: 2) is what believing in the WORK of the Lord Jesus Christ.
Believing in the PERSON and the WORK of the Lord Jesus Christ is what the Gospel Message is all about.
BELIEVING, that is placing one’s trust and confidence, in the Gospel Message is the ONE and ONLY way in which a spiritually dead soul can be born again (John 3: 5, 7).  Being born again is what enables the soul to enter in Heaven.
When anyone or any organization contradicts, adds to, takes from, or perverts the Gospel Message, the Church Age believer is commanded not to open the door, or worse, participate or do anything that would encourage such activity.  Such organizations include the many alternative Churches that have been established by <am-made, "religious" authority.
In these days of advancing technology, “opening the door of our house” would include what we choose to listen to (or allow others to listen to) on such things as the radio, television, cable television, satellite television, CD’s, DVD’s, smart phones and the Internet.
Much of these developments in technology are morally neutral, in that they are being used by both the Kingdom of God and the Kingdom of Darkness to promote their opposing agendas.
It is through such technology that many of the end time prophecies can now  be easily accomplished, that in previous times seemed more like science fiction. In a matter of seconds we can see what is taking placing virtually anywhere in the world and certain areas of outer space.
While this technology is being used to bring to completion the fulfillment of the Great Commission (Matt. 28: 19, 20) and the prophesied end of the Church Age (Matt. 14: 14), it is also being used to promote the agenda of the Anti-Christ and the Kingdom of Darkness, distracting and/or deceiving the whole world (Matt. 24:4/Rev. 12: 9).
* * *
Giving a g-r-e-e-t-i-n-g implies a offering a gesture of respect or fellowship, as seen in (1Pet. 5: 14 NASB).
“Greet one another with a kiss of love (1Pet. 5: 14 NASB).”
In the Eastern world, and in parts of Europe and Asia, giving a greeting might involve  addressing another by a title, a bow, a kiss on the cheek, etc..
In the Western world, it would be equivalent to offering a hug or a heart-felt handshake, as well as addressing others with an appropriate title of respect.
It’s great to have a friendly attitude towards other people, providing one has the spiritual discernment to avoid shaking the proverbial hand of the devil (or one of his spokespersons) in the process.
* * *
There are other ways in which one can “partner” with evil, evil  people, and  evil institutions.
One partners with the devil when he/she becomes the one who enables, encourages, condones, or facilitates sin in the lives of others.  Failing to speak up in fear of rocking the family boat disqualifies a born again believer from the life of discipleship (Luke 14: 26).
We partner with evil organizations by our attendance and encouraging others to do the same. 
An evil organization is one in which evil is promoted. Anything, in doctrine or in practice, that is contrary to the Word of God is evil.
There is evil being promoted and practiced in many of the “alternative” Churches that are the product of Man-made religion.  Many  involved with Christian religion will, among other things, regularly pray for "deliverance from evil," yet fail to discern the evil  with which that they are presently engaged in  within the walls of  their chosen denominations.  Religious people are infamous for having the ability to see the "speck" in the eyes of others, but can't see the "log" in their own (Matt. 7: 4, 5 NASB).
We partner with evil by displaying logos, icons, bumper stickers, etc. that promote human or religious viewpoints that are contrary to the Word of God..
We partner with evil by giving others or institutions our time, talents, and service.
We partner with evil  by providing them with logistical/ financial support.
As partners, we become participants in  the evil that evil persons and evil organizations produce.
Granted, the promotion of evil is often done in ignorance, but a bullet fired in ignorance can be just as lethal as a bullet fired with malicious intent.
Once the evil activity has been made unmasked, it is no longer a case of ignorance.
Sincerity does not justify our actions.  The very religious Pharisees believed with all their hearts that they were serving God by opposing the Lord Jesus Christ.  The Lord  Jesus Christ made it clear that there will be religious  persons  that will persecute true believers to their death while believing that what they do is a service to God (John 16: 2).
The deceptive part of religion is that it is projected as having the appearance of having come from God, and being what God requires.  Like any counterfeit, it must appear to be the real thing if the deception is going to succeed. 
Deception is working well for the devil.  Scripture (Rev. 12: 9) refers to  the devil  as the one who is deceiving the whole world.
While most religious people believe (or at least hope) there is a  Heaven  and that they are headed there,  Matt. 7: 13 teach that only a "few"  (the minority) will find the straight and narrow way that leads to life (Matt. 7: 14).
This leaves us with the ominous  truth concerning the final destination and eternal environment (Rev. 20: 13, 15) of the "many" (Matt. 7: 13), that is the m-a-j-o-r-i-t-y of those with whom we interact with on a global basis.  This may seem strange  to anyone who had the privilege of growing up in a Christian environment, but Christianity has NEVER been and will NEVER be the dominating human experience on a global level until after the Second Advent when the 1,000 year kingdom is established.  Scripture (Matt. 24: 14) teach that the Gospel Message will be made known to the world at large, not that all will come to believe it during  their time here on Earth.
Many people feel a sadness for those who are Orthodox Jews, having been so close to God, but face eternal damnation for rejecting the Person and the Work of the Lord Jesus Christ (Rev.20: 15).  Equally tragic, are those who are followers of Christian Religion (and not Christianity) who, as a result, are never born again (John 3: 5, 7).  Without a doubt, if the Rapture were take place in the middle of many worship services, there would be many left behind sitting in the pews and around the altars.  Just because one goes to a hospital does not mean that he/she is going to be healed.  Just because one goes to Church and touches all the bases of Man made religion does not mean that he/she has been born again and saved. 
Luke 12: 52  teach that even within a single household, there will be those who are saved, and those who will not be saved, even though in more cases than not, they ALL went through the same religious activity at one time or another in the course of their lifetime here on Earth.  There is no greater fool that the one thinks he/she is pleasing or serving God, when in truth he/she is partnering with evil and serving the interests of the Kingdom of Darkness.
The born again believer who becomes an advancing disciple KNOWS that there is a Heaven, and KNOWS that he/she is Heaven bound.  The advancing disciple has this confidence because he/she is aware that his/her salvation is not based on any religious activity that others had done to or for them, or any amount of human good or good behavior.  The advancing disciple's confidence is based on the knowledge of what God has done, is doing, and will do for the people of faith.  The people of faith are those who have been born again.
The more spiritually mature an advancing disciple becomes, the more he/she will be able to perceive the evil nature of the alternatives offered by Man-made religion or any other form of human viewpoint.
The advancing disciple will break off all past associations with evil that he/she engaged in, now being able to see how he/she had been deceived.  He/she will have no interest is forging any new partnerships with evil, WITHIN or outside of the Christian Community-at-large.