And for those of you who like to discuss how positive data can be used to support normative statements (on either side of the aisle) here's a very useful and interesting video (HT to Greg Mankiw).
I think this can be used a number of ways. But the most important lesson I would offer your students is "what data isn't being shown (on either side) and why?" Too often we (teachers and students) get caught up in an idea and neglect some aspect of the data that may enlighten. And just as often we add data that muddies the water. As always, I welcome your observations.