(Sigh.)
Did the rapist initiate force against my sister? Did my sister ask to be raped?
I think the answer is no.
OK, now, select the correct answer, if you can: the rapist is / is not justified in raping my sister under libertarian philosophy.
Better clarify before somebody gets all upset.
I think the answer to the first question is yes, and the answer to the second question is no.
For all you budding lawyers out there.