What is the dramatic purpose for the prayer meeting and for Howard’s testimony?

I think they reveal the hypocrisy of many conservative Christians in the town who pray for damnation of people with opposing views and throw logic out in exchange for hysteria. At the prayer meeting Brown calls upon God to call down hellfire and vengeance upon Cates, to make him writhe in damnation, when finally Rachel cries out to stop him. In response, he calls upon God to curse those who ask for grace for sinners. Finally, Brady rushes over and grasps Brown's arm. He says that it is possible to be so overzealous as to destroy that which you hope to save. He quotes the wisdom of Solomon, "He that troubleth his own house...shall inherit the wind." He reminds him that the Bible urges forgiveness and sends the townspeople home.

Two days later, in the hot courtroom, thirteen-year-old Howard is on the witness stand. Brady questions him about what Mr. Cates taught. According to Howard, Cates taught that at first the world was too hot and over millions of years, little bugs grew to bigger bugs and climbed out of the water. Then fish and reptiles and mammals, including man, came along. And out of what Brady calls "this mess," man evolved from "Old World Monkeys." But, Brady asks, in all this talk of "Evil-ution," did Cates ever mention God or the miracle of Genesis. Howard says no. And though Drummond objects to his speech-making, Brady proceeds to pontificate to the jury about the poison the "Evil-utionists" peddle and the need to mete the full penalty of the law to Cates so that the world will call the courtroom blessed.