If you read the update on the site you linked to (http://www.christianliferesources.com/news/rape-pregnancy-and-the-akin-controversy-8741) the author says, "I have yet to see a study that demonstrates some sort of contraceptive effect from a rape." Now he does go on to hypothesize that it could happen, but the important thing is that there is no science or study showing it, so it shouldn't be cited as a reason for being pro-life.
Akin is bring distorted, particularly on the "legitimate rape" quote. But it behooved him to speak more clearly and avoid the issue. The rape/abortion trap has been used by the media and democrats for decades now, a good candidate can't fall into it.