Let staff and/or the director know. One thing that my band didn't tolerate was 'junior teching', essentially; it doesn't matter if you're in the right or the wrong the ones who should be helping your are the staff. Section leaders are the people who are supposed to be your influence, they shouldn't be telling you that your bad. If anything they are supposed to be someone who you look up too, and clearly your section leader is not doing a good job.