Well, when someone supports the subhuman, inhuman and inhumane brutal dismembering murder of beautiful, healthy, innocent and defenseless human babies you simply cannot expect them to base their view on anything even near the realm of logic (or ethics, for that matter).
The main argument of the pro-abortionist with whom Greg Koukl speaks is that unless you are personally doing something to help those babies after they are born then you have no right to be pro-life.