Wow, this is an intense thread. I hope you will share your fantasy with your therapist. I'd agree especially with sister that your fantasy is about wanting to share overwhelming feelings with your therapist. You just don't know a healthier way of sharing them and finding release (catharsis? is that the word?). I expect he could help you find a way to make these things verbal rather than violent. I hope you'll choose to talk about it with him.

Sidony