The killed receptionists' pictures would likely convince any one that killing receptionists is wrong, if they didn't already believe that. Only a sadist would decide to change TO believing it was okay to kill a receptionist, based on a gruesome picture. Of course, most people already know it is wrong.
In a similar way, pictures of killed fetuses might convince fence-sitters that killing fetuses is wrong. And, in a similar way, gruesome killed-fetus pictures are highly unlikely to "convince" fence-sitters that killing fetuses is all right.
I saw you other post where you did a break down of the groups. You were very realistic in your break downs. You correctly assume that some fence sitter may be swayed.
How much more Pro-choice to you think the few truck converts will become on the average using a scale of one to ten?
What is your guess at the additional percentage of people who will now:
Be more Pro-choice but never do anything about it?
Vote more Pro-choice in the polls only?
Vote more Pro-choice in the voting booths only?
Make some effort to persaude others to become more pro-choice?
Become highly active Pro-choicers?
Not have an abortion they might have had?
Will revert to their old beliefs when the conditioning has worn off?
There is a good chance that the images will trigger a cognitive dissonance. The fence sitter may have to give up some deep rooted beliefs to accept that abortion is murder. Rather than giving up those beliefs, they will be mentally forced to strengthen their belief that abortion is not murder.
The nature of the deep rooted beliefs may include having had an abortion or having supported an abortion (husband, boyfriend, mother, father, sister, brother, friend, etc). For anyone of these people to accept that is abortion is murder, they will have to accept that they participated in a murder.
It may include having had a sibling aborted. In this case they would have to believe their parents are murders.
They may have friend who had an abortion. In this case they would have to accept that their friend is a murder.
They may have actively supported the Free Choice movement. In this case they would have to internalize that they actively supported murder.
The well known effect of cognitive dissonance is that the person does not remain as they were. Accepting the concept that would destroy the deep beliefs is so horrible that they must become more adament and vocal about the whole issue.
In other words, the images may very well convince a fence sitter that killing fetuses is all right.