Interesting logic
You make it sound in your post as though the radical Islamists are more angered with non-believers than Christians and yet, if you look through history, Muslim persecution has primarily been a result of Christian militarism.
Yeah, I wouldn't feel necessarily safe walking through the streets of a Muslim area in Yemen or Syria but my fear would mostly be generated by the distaste they have for Americans not American atheists.
However, I would be willing to bet I would generate a whole lot less hatred worldwide among Muslim people by walking around with a Charles Darwin t-shirt than one depicting Jesus.
Art