Mark 3

1Another time he went into the synagogue, and a man with a shriveled hand was there. 2Some of them were looking for a reason to accuse Jesus, so they watched him closely to see if he would heal him on the Sabbath. 3Jesus said to the man with the shriveled hand, "Stand up in front of everyone."

These are his accusers.

4Then Jesus asked them, "Which is lawful on the Sabbath: to do good or to do evil, to save life or to kill?" But they remained silent.

5He looked around at them in anger and, deeply distressed at their stubborn hearts, said to the man, "Stretch out your hand." He stretched it out, and his hand was completely restored. 6Then the Pharisees went out and began to plot with the Herodians how they might kill Jesus.

7Jesus withdrew with his disciples to the lake, and a large crowd from Galilee followed. 8When they heard all he was doing, many people came to him from Judea, Jerusalem, Idumea, and the regions across the Jordan and around Tyre and Sidon. 9Because of the crowd he told his disciples to have a small boat ready for him, to keep the people from crowding him. 10For he had healed many, so that those with diseases were pushing forward to touch him. 11Whenever the evil^[a] spirits saw him, they fell down before him and cried out, "You are the Son of God." 12But he gave them strict orders not to tell who he was.

...

22And the teachers of the law who came down from Jerusalem said, "He is possessed by Beelzebub^[c]! By the prince of demons he is driving out demons."

This is their accusation.

23So Jesus called them and spoke to them in parables: "How can Satan drive out Satan? 24If a kingdom is divided against itself, that kingdom cannot stand. 25If a house is divided against itself, that house cannot stand. 26And if Satan opposes himself and is divided, he cannot stand; his end has come. 27In fact, no one can enter a strong man's house and carry off his possessions unless he first ties up the strong man. Then he can rob his house. 28I tell you the truth, all the sins and blasphemies of men will be forgiven them. 29But whoever blasphemes against the Holy Spirit will never be forgiven; he is guilty of an eternal sin."

30He said this because they were saying, "He has an evil spirit."

This time, this is his response -- he taught them with Truth. It is not just truth about the casting out of demons, but about the Holy Spirit of God, and of condemnation and guilt and righteousness and forgiveness ... teachings that do not come from unclean spirits. He makes the claim here "You accuse me of casting out these spirits by the power of Satan, but you blaspheme the Holy Spirit when you do so." He is making a claim that he is doing this by the Spirit of God. He backs up his claim by teaching the Good News of the merciful forgiveness of sins (which no unclean spirit would utter).

Mark 11

27They arrived again in Jerusalem, and while Jesus was walking in the temple courts, the chief priests, the teachers of the law and the elders came to him. 28"By what authority are you doing these things?" they asked. "And who gave you authority to do this?"

Again the source of his power is questioned.

31They discussed it among themselves and said, "If we say, 'From heaven,' he will ask, 'Then why didn't you believe him?' 32But if we say, 'From men'...." (They feared the people, for everyone held that John really was a prophet.)

33So they answered Jesus, "We don't know."
Jesus said, "Neither will I tell you by what authority I am doing these things."

In essense he told them, "I don't need to defend myself against you." He backs this up later when he declines to defend himself to Pilate. In general, this is his response to accusers in the scriptures, as best I can tell: "I am doing my Father's business. If you question me, you do not know the things of God" and also, "The Spirit of God (who is the Spirit of Truth) testifies to these things."