Why do a lot of women who practice BDSM have fucked up fantasies about getting raped, peeing on people amd getting peed on, and various other degenerate things?

Moreover, I find that people into this stuff are usually pro-Liberal, Femenist, Gender bending, etc.

Were they abused as children or something?

I can understand a foot fetish or something innocent like that but some of these fantasies are incredibly fucked up.