What could I say in an introduction to the text of Father Coughlin's "Address to Townsendites?"
In an introduction to this speech, you should talk about the following two main things.
First, you could talk about the historical context of the speech and who the author was. You should talk, of course, about the Great Depression and the problems that came along with it. You should talk about the basic efforts of the New Deal to use government spending to fix the economic problems. You should then talk about Father Coughlin and mention that he was a critic of the New Deal.
Second, you could move to a brief introduction of Coughlin's ideas such as are seen in the speech. You could talk about how he was a right-wing populist who was suspicious of big businesses but was also very opposed to anything that smacked of communism in his eyes.
This would give a reader a basic idea of what to expect in the speech and how to understand that speech in context.