Why did Stephen lecture the priests and his accusers before his death?


Then the high priest asked Stephen, “Are these charges true?”
To this he replied: “Brothers and fathers, listen to me! The God of glory appeared to our father Abraham while he was still in Mesopotamia, before he lived in Harran. ‘Leave your country and your people,’ God said, ‘and go to the land I will show you.’ Acts 7:1-3
            If you were going to die by an angry mob, wouldn’t you do anything to delay the inevitable?  Possibly, but Stephen wanted to lecture his accusers with facts from the Bible.  So he gave a detailed history from Abraham to Moses, wrapping up with David and Solomon, about God’s purpose and power in the Bible and the opposition God always faced by stubborn people. 
 “You stiff-necked people! Your hearts and ears are still uncircumcised. You are just like your ancestors: You always resist the Holy Spirit! Was there ever a prophet your ancestors did not persecute? They even killed those who predicted the coming of the Righteous One. And now you have betrayed and murdered him—you who have received the law that was given through angels but have not obeyed it.” Acts 7:51-53
            Here you go again was Stephen’s theme—killing God’s people.  And then they killed him, following in the footsteps of their ancestors.