degsme:

Most rape IS about power and subjugation. Fighting back is an indicator the victim hasn't been subjugated enough. It will almost always escalate the violence of the attack.

That is, unless the victim fights back with overwhelming counter-violence, of the sort that (at least temporarily) destroys the aggressor's ability to inflict harm. (That's why they say, "You don't shoot to wound; you don't shoot to kill. You shoot to _stop_. If he dies from it; he dies.")