Female sexual arousal = defense against rape?

Holy non sequiturs, Batman! Read it here. Excerpt:

'The findings confirm a long-held belief among sexual researchers that has apparently not been studied in any depth before. The results provide new insight into the evolutionary development of human sexual responses, suggesting that women may have evolved a more responsive sexuality to help them cope with forced copulation.

Established ways of assessing sexual identity are more invasive. For men, it involves wrapping the penis in a device that measures expansion in response to erotic stimuli. For women, it is the insertion of a vaginal probe that assesses changes in the amplitude of the vaginal pulse.
...
The findings support the idea that sexual response has different biological functions in men and women. For men, an important function is to facilitate erection and penetration. For women, the function is to stimulate lubrication and prevent genital injury in case of penetration -- a response that may have developed early in evolutionary history in response to episodes of rape by males.'

So lubrication of the vagina in females is a defense against vaginal trauma inflicted by rapist males. Um, what? You mean it doesn't happen because, well, the woman might just get aroused by *gasp* the idea of having sex with a *gasp* man and vaginal lubrication makes this all the more possible? I don't know where the author got his ideas about sexual dynamics from but I doubt they came from common bloody sense.