Here's the reason rejecting the rape/incest exception is so unbelievably stupid: r/i exceptions account for only 1% of all abortions, with life-of-mother exceptions making up 0.5%. What idiot would see the abortion rate in this country drop from 800,000 to 4,000 per year, but would NOT accept seeing it drop from 800,000 to 12,000 per year as a stepping-stone to 4,000 per year?
Here's another reason it's stupid. Yes, people should only have to pay for their own mistakes. That's why we reject elective abortion: you spread your legs by your own choice, now you have to bear the consequences. But women who are raped or pressured into incest didn't make that choice. So there is a karmic argument that, hey, maybe we should make an exception here.