Boy with ADHd causing problems what to do?

There is this boy in my school (Senior year) who has ADHD and seems to get away with everything right so he calls people Nazis etc and makes people burst into tears and nothing gets done also we are going on a school trip for a week and he is dictating what room hes in and group even though it means all of our groups being changed about to suit him,ive tried reasoning with him but all i get is "you fat communist Nazi Hitler f***er etc" i dont want to seem to be bullying him but how can i sort this