Rape is not always about being sexually attracted to someone, but about power and control. Women are raped regardless what they are wearing and how they act, and so it therefore may be quite limited what society can do to correct this.

'Thunder thighs' is an alliteration :)

'Thunder thighs' is mentioned again, towards the end of the text. Perhaps they are trying to emphasize something.

'Thunder Thighs' is alliterative. 

I think the dark color of the legs is supposed to signalize somehting. It makes them appeaer strong, as opposed to if they were ligher.