John is writing to the disciples of the time and trying to encourage them to live in the ways that they had been taught. They had learned that Jesus is the Christ and that they should love him by doing what Jesus had commanded. They had learned the truth, but now they must walk in that truth.
But it is possible to deny the truth of Christ. Either at that time, or in our day, the truth of Christ could easily be denied, leading many people astray, and that is what happens in these days. Many people have been blinded as a result of their denials, whether they be the “learned”, Muslims, Buddhists, Hindus, or many, many others. They have denied that Jesus is the Christ. So John has some specific warnings for the believers so that we keep a watch out for these people and their teachings:
But you have an anointing from the Holy One, and all of you know the truth. I do not write to you because you do not know the truth, but because you do know it and because no lie comes from the truth. Who is the liar? It is whoever denies that Jesus is the Christ. Such a person is the antichrist—denying the Father and the Son. No one who denies the Son has the Father; whoever acknowledges the Son has the Father also.
1 John 2:20-23
We have a desire within us to go our own way. We desire to be our own ruler, our own king. But John is writing, he says, so that we that know the truth of who Jesus is will not fall away but will continue in what we know. We do not want to be influenced by those who lie through their denials of the identity of Christ. We do not want to fall under the influence of the antichrist, but instead know the Son, and therefore we will know the Father.
John says that whoever denies that Jesus is the Christ is the antichrist. Let us continue on our path to proclaim Jesus as the Christ, the Messiah who was to come into the world and is yet to return.