Atheists, How can I convince my best friend that Bin-Laden is not a Martyr?

I found out that my best friend deems bin-laden a martyr and a good guy, he even made his Facebook [lame site] avatar the guy's image. Lots of confused thoughts and furious doubts are shaking my mind that I can't think clear right now, what do you think is the best next step to go through this smoothly?