Even though I am firmly opposed to abortion, I do see circumstances where it should not only be necessary, but recommended. The rape scenario is one of those circumstances.
I tend to agree, but I can also respect those who see the issue differently. For someone who believes that a human fetus is a living person and should have the same rights as you or I, it's quite logical to not make the sorts of exceptions we're talking about. For that person, so accept such an exception would effectively mean that the circumstances of your conception determine whether you get certain rights in our society. We don't deny someone a single right after they are born if they happen to be the child of incest or rape, so why deny the right to life to them before being born? Again, assuming someone who believes that such a right should exist prior to birth, that is.
IMO, the problem with Akin's statement wasn't so much with the statement itself (although it was at the least horribly stated), but the fact that it's not really his position. He was trying to sidestep the issue of the exception by trying to argue that it doesn't happen very often (a dumb argument all by itself), when he should have simply stated that he doesn't believe that an unborn child's rights should be any different based on how it was conceived. It would have been the more honest answer.
Additionally, I also can see that as a counter to Joph's argument, many on the left use the rape exemption as a lever to ensure that elective abortions are kept as widely available as possible. More or less for exactly the reason that it places the anti-abortion crowd in the position of either assailing the otherwise popularly held exceptions for rape and incest *or* accepting what really is a hypocritical position. What they really want is to pass some sort of legislation (which would require a constitutional amendment given the Roe v. Wade decision) codifying a fetus' right to life. The exception cases make that more difficult, and I imagine there's lots of disagreement on how you proceed without dealing with those.