I'd like to offer a differing opinion.

I listened to NPR on the day it broke out, and here was the full quote:

It seems to me, first of all, from what I understand from doctors, that’s really rare. If it’s a legitimate rape, the female body has ways to try to shut that whole thing down. But let's assume that didn't work or something. You know, I think there should be some punishment, but the punishment ought to be of the rapist, and not attacking the child.

Yes, it's ignorant, but the point is that he never stated it as a fact. While everyone is focusing on "legitimate rape", the actual point he was trying to convey is that "punishment ought to be of the rapist, and not attacking the child". You might disagree with it, but remember that he's not the only one holding that position - Paul Ryan, for instance, supports banning all abortion, including in case of rape and incest.

So is it a "controversial remark"? Yes, because it sparked the whole abortion debate, which was not really being discussed at that time.

So is it a "gaffe"? I think so - he said something he should not have said because he did not know what he's stalking about.

And let's face it - while it would be nice if politicians knew the facts about everything they voted on. But they don't. They just know what their lobbyists laid it out for them. Take net neutrality, for instance, or software patents.