It is alas against policy around here to reproduce a chart, but you really do want to click through and look at "Jenny McCarthy Causes Autism" over at Mostly True Stuff (via Drezner).
I have very little to add, but I couldn't resist a link to it. The clincher? "The blue line is made up."
Recommend using it next time you're teaching correlation vs. causation. Except, I suppose, for the part about it being made up.
On the other hand, one could argue that a made up line beats long-ago discredited data.