1 John 2:2 And he is the atoning sacrifice for our sins, and not for ours only, but also for the whole world.
1 John 4:2 By this you know the Spirit of God: every spirit who confesses that Jesus Christ has come in the flesh is of God, 1 John4:3 and every spirit who doesn't confess that Jesus Christ has come in the flesh is not of God, and this is the spirit of the antichrist, of whom you havheard that it comes. Now it is in the world already.
1 John 4:9 By this was God's love revealed in us, that God has sent his only born Son into the world that we might live through him.
1 John 4:14 We have seen and testify that the Father has sent the Son as the Savior of the world.
Christians should certainly confess and thoroughly believe that Jesus did indeed come in the flesh, for which purpose was to offer that sinless flesh, his sinless humanity, in which was life, in sacrifice to God for the church and the world of mankind. (Matthew 20:28; John 6:51; Luke 22:19; Romans 3:25; 5:8,12-19; 1 Corinthians 15:21,22; Ephesians 5:2; Titus 2:14; Hebrews 10:5,10; 1 Peter 3:18; 1 John 2:2; 4:10) John emphasized that Jesus had come in the flesh, since this is the whole basis of the atonement as set forth in the New Testament.
On the other hand, if Jesus still has that flesh, then he never really sacrificed that flesh, and thus such a teaching would deny the central purpose for which Jesus became flesh.