We don't say they are lying. God is Jesus' Father and Jesus is the Father's Son but only in the natural sense. Spiritually, Jesus is God, that's why His Name was "Everlasting FATHER" (Isaiah 9:6), also Jesus is Emmanuel which is GOD WITH US (Matt 1:23).
Jesus specifically came to earth to SHOW US THE FATHER. So Jesus said, "If you've seen Me, you've seen the FATHER ALSO" (John 14:7)
Jesus is IN THE FATHER and the Father IS IN JESUS (John 14:11) that's why Jesus and His Father are one (John 10:30)
Jesus Himself said He was God and that's why the Pharisees and Leaders tried all the more to kill Him (John 5:18) and hated Him.
In addition, Jesus said, "I and My Father are one" (John 10:30)
Jesus said, "I am IN MY FATHER and My Father IS IN ME" (John 17: 21 & 23)
Spiritually Jesus is God but God is a Spirit (John 4:24) and a Spirit is invisible so God could not come to earth as a Spirit to be crucified for our sins, So instead, God put Himself into a body (God in flesh (John 1:14) and came to earth as Jesus Christ His own Son, who proceeded out from the Himself. (John 16:28, 30 John 17:8)) God is Spirit and He is Holy, so God is also Holy Spirit who also proceeded out from Himself to come here after Jesus went back to heaven.
God is powerful and can do all things, even splitting Himself up into Father, Son and Holy Spirit so He can be everywhere at once. Jesus came in the restriction of a flesh and blood body so Jesus could NOT be everywhere at once whilst He was in human flesh, but when He returned back to His Father, He sent His Holy Spirit here who could be everywhere at once and that's why Jesus said, "I will not leave you orphans, I will come to you" Jesus came to us by His Spirit, the Spirit of the Father, the Holy Spirit because these three are one.
God came here in the form of Jesus Christ (God in flesh ) - Emmanuel, which being interpreted means God with us - so that He could be with us and everywhere at once.
King David said, "Where can I hide from you? If I ascend into heaven, you are there, and if I make my bed in hell, you are there" so King David understood that God was Father, Son and Holy Spirit, - these three bear witness in heaven, and THESE THREE ARE ONE (1 John 5:7)