Key themes important to all of the fiction of Hawthorne relate to hypocrisy of Puritans and the 'dark side' that is evident in all of us, no matter how seemingly pious or holy. You might want to explore these issues by an attention-grabbing statement like 'Piety is only skin deep.' This would allow you to investigate these themes in this tale and analyse how Hawthorne scratches beneath the surface of the human psyche.
Since argument, or persuasive writing makes use of rhetorical questions, could you not use such a question about Puritanism? (Afterall, Hawthorne seems to be casting aspersions upon this belief, himself.)
For example, Is man so depraved that sin is unredemptive? Essentially, Brown, who is so confident that he is one of the Elect that he can leave his wife Faith and go into the primeval forest, feels he is. But, once his faith is lost in the forest's Black Mass when he sees his wife Faith dressed as a proselyte, he views his fellow man as a sinner, depraved, and not one of the Puritan Elect.
(Be sure to do some research on Puritanism before embarking upon your argument)
If you like plays, you might use Miller's "All My Sons" and ask whether Joe Keller's assertion that what he did was what everyone else did, and is nothing he should be singled out for was true. If it's a long enough essay, you might want to expand the question to explore the issue of profiting from war in World War II or even look into allegations that there are many companies making large sums of money in our present wars, Halleburton (sp?) for example.
If you can't get an information, you could still explore the moral implication of Joe's position.
You might ask about Hawthorne's views of the Puritans as seen in "Young Goodman Brown" and explore the reasons for the negative portrayal. You can argue that his negative perspective on Puritans stems from one of his ancestors, Judge Hathorne (grandfather?), served as a judge during the Salem Witch Trials (see The Crucible). Since nineteen innocent people lost their lives as a result of the hysteria, Nathaniel Hawthorne wanted to disassociate himself from his ancestor, and one way he did that was by adding a "w" to the spelling of his name. As a result of the Salem hysteria, Hawthorne's opinion of the Puritan society was jaded.