4chan, anon is only a 50% capecel

Not a kangaroo court at all. Imagine if Professor Dumbledore had used Avada Kedavra on one of the students who had misbehaved, then in his defense used the argument that "well it doesn't matter because the student had drank a whole lot of Alihotsy Draught before I used Avada Kedavra on him. How credible do you think a defence like that would be and how would Hogwarts (both teachers and students) react if he was found not guilty because of it?