Simply put, in their minds it's patriarchal control of a woman's body to make her dress in a respectable way. Driven out today, you get women doing things and wearing things that would have been obscene back in 1972 for ANYONE (men and women), girls going wild, porno participation being widely accepted by women and more harder core (the Hooters concept wouldn't have flown in 1972) and sowing societal acceptance by decrying "slut shaming". Remember it's misogyny for women to be held to any kind of standards by anyone, since those standards represent patriarchal control.
Next time you see that Girls Gone Wild commercial just think of what I hear when I see them: "I am woman hear me roar in numbers too big to ignore.". That's today's feminism in action.
Side question: I wonder how possible it would be to find out the sales figures for Playboy Magazine in 1972 compared to today. I would guess it's much higher today for this reason and others.