Agreed with lookingforwater that people's stated motivations don't always cover the full range of what's going on inside their heads. I wouldn't dispute that acting as if pro-life people don't truly believe their own words isn't helpful, and in lots of cases isn't accurate, but sincerity isn't quite the same thing as honesty. In particular, the correlation between anti-abortion stances and anti-feminist, or downright misogynist, ideas is strong enough to suggest that there's some connection there. Pulling one example out of the ether, I heard someone whose views I often respect and agree with described women who seek abortions as 'Sex-and-the-City wannabe sluts' the other day. I'm absolutely sure that this person is genuine about her pro-life views - she really does believe abortion is murder. But when 'sluts' is the first place your brain goes when you're talking about the issue, you might want to examine your motives a little more carefully.

I was going to talk some more about the connection between anti-abortion stances and anti-women-controlling-their-own-bodies ideals, but Ampersand put it better (http://www.amptoons.com/blog/archives/2006/03/21/why-its-difficult-to-believe-that-anti-choicers-mean-what-they-say/) (and in handy chart form!), especially in relation to the debate in the US.