I compare this generation to children who are uninterested in dancing to the tune of flutes or in mourning at the sound of dirges. The Gospel passage for today presents us with a visibly angry Jesus. Jesus is angry at the blatant display of indifference by a section of his listeners. When he appeared on the scene, compared to his cousin John the Baptist, he brought a relaxed approach to religion (cf. Mark 2:18:  why do John’s disciples and the disciples of the Pharisees fast while yours do not?) Jesus had hoped that his inclusive approach when it comes to treating people would be embraced with open arms. But after being in the scene for a while, he came to realize that the people’s reception of what he was about fell short of his expectation and hopes. Perhaps he had opened his arms too much. It was one thing to preach the unconditional love of God from the pulpit, but it was a different thing altogether to demonstrate this in action (as Jesus was apparently doing as he kept the company of tax collectors and sinners). 
Jesus was being accused of reaching out to those who were doomed. He was accused of giving hope to those who had been told there was no hope for them. He was being disparaged for revealing the merciful and forgiving face of God to the world. He took offence at those who were pointing accusing fingers at him because these were the very people who had been praying and longing for the coming of the kingdom of God. He took offense because here he was ushering in the kingdom and instead of being embraced, the people chose to reject both him and what the kingdom was offering. He looked at them and made a conclusion that they did not know what they wanted (or what they were praying for). Their blatant display of indifference will be their undoing and as such their blood will be on their heads.