"This is how everyone will know that you are my disciples, if you have love for one another." - John 13:35 (NIV)
A genuine Christian would never totally shun a disfellowshipped family member or life-long friend who walked past them. Christ's true disciples would not walk buy and look the other way, refusing to even say a greeting. The admonition in 3 John is clearly only meant for persons who are apostates from Christianity, ie, who outspokenly speak against Christ and God, not mere immoral persons or persons who leave a religious organisation but still profess faith in God.
The exhortation in 3 John not to even say a greeting to such a person is utterly misapplied to offences under 1 Cor 5 by the Watchtower Society - a clear abuse of scripture.
Jehovah's Witnesses fail to live up to John 13: 35 by their willingness to symbolically kill family members and former friends by totally shunning them. This is anathema to the message of love and mercy that Jesus preached.
Also, the judicial arrangement of disfellowshipping persons for sins under 1 Cor 5 (and similar 'moral' offences) is also a gross distortion of the Christian message of love and forgiveness that true disciples of Christ should show for one another, through thick and thin. Disfellowshipping should be an extreme measure of last resort to remove persons from the congregation who are thoroughly hardened and unrepentant. No matter how many times a person sins, if they express sorrow and a desire to change, they should never be shunned like a leper. Jesus said to forgive up to 77 times. Such persons should be reproved/admonished but helped and supported to gain the victory over sin. And even if they are thoroughly hardened and unrepentant (for the present moment) they should be given the same courtesy and kindness that all Christians should show to anyone, including those without faith and their enemies, as Jesus taught us. That is the hallmark of genuine Christian love. Only rank apostates against Christianity itself should be totally shunned.
Because JW's so harshly and totally shun 'their own' (congregation members and family members) who have been disfellowshipped, and abuse and twist scriptures to support that merciless position, they are easily dismissed as not fulfilling John 13:35.