(Matthew 3:16, 17) Why do Christians insist that Jesus is talking to himself here?

That is stupid for a person to think. These scriptures is about the baptism of Jesus. Jesus and God are not the same, Jesus is the Son of God.In this scripture, God is speaking from heaven. How can Jesus speak from heaven and be on the earth at the same time? Man's traditions makes God's word void. Any Christian that is saying Jesus is talking to himself needs to study the word of God more before speaking untruths..."16And Jesus, when he was baptized, went up straightway out of the water: and, lo, the heavens were opened unto him, and he saw the Spirit of God descending like a dove, and lighting upon him: 17And lo a voice from heaven, saying, This is my beloved Son, in whom I am well pleased". - Matthew 3:16-17