I believe that you have the right to your feelings about anything. It isn't just you who would find those images graphic and disturbing. I would find them very unpleasant. Many things trigger different people. Autism or not. It may be that you just need to process your feelings such as crying to release the stress. That is OK. You are entitled to your feelings. That poster may have reached you in a deeper way and that is OK. This society has become so insensitive and I can see how that may affect many in differing ways. Try to find ways to cope by deep breathing or use a distraction. You are doing pretty well also dealing with the mounting stress of school. Best wishes with your schoolwork as well.