1 Jn 2:22 Who is a liar but he that denieth that Jesus is the Christ? He is antichrist, that denieth the Father and the Son.
1 Jn 4:3 And every spirit that confesseth not that Jesus Christ is come in the flesh is not of God: and this is that spirit of antichrist, whereof ye have heard that it should come; and even now already is it in the world.
2 Jn 1:7 For many deceivers are entered into the world, who confess not that Jesus Christ is come in the flesh. This is a deceiver and an antichrist.
While false teachers may also in included, I cannot accept they are the only ones these texts are describing.
This is a relatively new understanding I have from the Bible (if you had asked me a month or so ago, I probably would have sided with you in addressing who "antichrist" referred to), but particularly considering the implication of 2 John terms of "going out", it seems that these passages are referring to those believers within the community who "go out" and preach a false gospel. Whether 1 John, 2 John, 2 Thessalonians, or Revelation, the context of "false teachings" and "false teachers" seems to be a clear and present issue to deal with.
Just a thought,