Being ratted out for stupid shit makes me so damn angry especially when you haven't done anything to deserve it.
Have you looked at this from the brother's perspective? He is naturally protective of his sister and wants to shield her from harm. He sees something brought into his house that he has been told is harmful. He does what any reasonable kid would do, which is go to his parents. Her parents reacted quite reasonably. You brought an illegal substance into their house, putting both their daughter and them at risk legally, plus exposing their daughter to something they see as very bad. Plus, you are a stoner kid. Not many teenage girls' parents want their daughter dating a stoner.
I think you are overreacting. You are lucky they didn't call the cops. I would have done exactly what their parents did and evicted you from my house. At some point you will hopefully learn that there is more to life than getting stoned, and that there is a time and place for everything.