When Drummond maneuvers his Christian Fundamentalist opponent to testify on the stand and proceeds to destroy any credibility in the literal interpretation of the Bible while showing the need for the freedom of thought.
Hornbeck's response as well. Drummond says he'll die alone and nobody will be there. Hornbeck replies that "You're wrong, Henry. You'll be there. You're the type. Who else would defend my right to be lonely?"
When Brown goes off the deep end and condemns Rachel, it's Brady of all people who calls him out on it.
"TELL THEM WHAT YOUR FATHER REALLY SAID!"
Drummound, challenged to say if he considers anything holy.
Henry Drummond: Yes. The individual human mind. In a child's power to master the multiplication table, there is more sanctity than in all your shouted "amens" and "holy holies" and "hosannas." An idea is a greater monument than a cathedral. And the advance of man's knowledge is a greater miracle than all the sticks turned to snakes or the parting of the waters.