Rather than talk about the 99.9% and the intrinsic value of human life as Bachmann and Santorum had in the GOP primary season, Akin is uttering the words "legitimate rape" and talking nonsense.
What he probably meant to say was exactly what you have pointed out, which is that the pro-abortionists use rape as their big argument, but in practice, the vast, overwhelming majority of pregnancies that are aborted do not come from forcible rape.
But anybody who is that poorly spoken and thoughtless doesn’t belong in politics, and the GOP should replace him immediately with another candidate (if they have one).