Apparently, a large proportion (the vast majority) of people practicing BDSM were abused in some form as kids.

Huh, I've never heard that from a kink-positive or kink-neutral person before, although I've heard it from the "Those kinky people are all fucked in the head and need to be in therapy For Their Own Good" fraction, and immediately discounted it because of the source, and because it runs counter to my own anecdotal experience. Interesting!