Rationality is just one mask. We have a whole closet full of masks. There's the happy one, the sad one, the mad one. And everything in between.
Just when you think you know what crazy is, someone will pop up and surprise you by doing some even crazier shit. You can't put a limiter on the craziness.
Add in a dose of hate, lots of stupidity, and serious weaponry, and well, the crazy can just get horrifying...