When Hans was being attacked you were unable to help him, when you killed him, Hans was already dead. It doesn't matter if you were busy while he was being attacked, but you cannot help dead people, you can only help them while they are alive and you are near them. You can not claim revenge for your friends, infraction was valid, appeal denied
EDIT: However, you were issued a 3 point infraction, which might be lowered considering your infraction history. I will have a talk with the punishing staff and update it
EDIT#2: Your 3 point infraction has been lowered to a 2 point infraction.