The message on this sticker is one that has always creeped me out. Of course, the main problem with the slogan is that it begs the question regarding the humanity of the unborn. Since the unborn is unquestionably a human being, the "choice" that the slogan speaks of is something that we would never "trust" a woman to do to her born offspring. Our argument is that abortion itself is an act which kills a human being, not something that avoids harming a child.
However, the implication of the slogan is very creepy. If you allow me to kill my offspring at an early stage of development, and then you can trust me not to harm any of my surviving children when they are older. If you don't allow me the choice to kill it when it's young, how can I be trusted to take care of any other children?
It also seems that the slogan is missing a question mark.