Have you noticed how abortion proponents always seem to come up with amazingly strained theories about opponents' motives--they hate sex, they want to control women, etc.? Abortion opponents say they believe that unborn children are human beings with the right to life. One may disagree, but that belief is an entirely straightforward and reasonable explanation for why someone would take an antiabortion position.
Apparently the pro-abortion side fears if it acknowledged that position is sincerely held, that would be tantamount to acknowledging it may be true.
If you read pro-choice blogs, you'll notice that in recent years they rarely ever make arguments regarding the prolife position and attempt to show how it is wrong or illogical. Instead, more and more they focus on trying to position prolife individuals, prolife politicians or the prolife movement in a way where they can then claim the only real reason for an opposition to abortion is misogyny.
You could call it the Marcottization of the pro-choice movement.