So basically, everyone here has some sort of mental disorder. I really appreciated in this film Lynch actually tried to make a concret story out of it :p
Love=Power, being loved=master. SM is a metaphor for mundane reality, normality; being a wife&mother, a female eunuch, is much worse. Ties, double-edged sword, things you own end up owning you. The tortured turned into torturer, ex-slave is the strictest master.