BDSM scenes work as ritual and not just comparatively, some practitioners intentionally structure their practice as a religious path. BDSM works as spiritual expression because it taps into three of the most primal, human forces: pain, power and, usually, sex.
Pain is the most familiar and universal characteristic of all human experience. It is a sensation that is inexorably bound with mental and cultural experiences and is often accompanied by an intellectual or emotional judgement. Pain is not the same as suffering. Suffering is not a physical sensation but an emotional reaction to any number of causes, some entirely painless. Pain can actually be a solution to suffering, a psychological analgesic that removes anxiety, guilt, and even depression.
You have me thinking. I will post a reply as a separate entry.