After the temple guards refuse to arrest Jesus, the Pharisees seem to go nuts. They yell at the guards, they curse the mob, and they say (wrongly ) that no prophet could come out of Gallilee (Jonah did). Then, as now, that's what happens when the Middle East authoritarian feels his iron grip on the people being pried loose by a force he does not understand.
So, the gloves come off. Way off. And it must be said, on both sides! When their Messiah stands before them and says, "I am the light of the world, whoever follows me will never walk in darkness, but will have the light of life," they just "lawyer up": "here you are appearing as your own witness, your testimony is not valid."
Jesus then warns them three times they will die in their sins, "if you do not believe that I am the One I claim to be." Three times he calls them children of the devil, whom he describes as "a murderer from the beginning, not holding to the truth, for there is no truth in him. When he lies, he speaks his native language, for he is a liar and the father of lies."
They say in effect "so's your old man" by calling him demon-possessed (twice). And then when their Messiah stands before them and declares, "before Abraham was born, I Am!" they pick up stones to stone him. At the beginning of John 8, Jesus prevents the stoning of an adulterous woman. At the end of John 8, He Himself is nearly stoned by an adulterous generation.
In John 8, Jesus is more Malcolm X than Martin Luther King, more fiery prophet than patient reformer. The power structure of Israel has no place for a Messiah it cannot control. The inevitable Final Break has been made. Jesus has an appointment with Gethsemane, Golgotha and the Garden Tomb.