I respectfully suggest that the discussion is sufficiently charged that just mentioning "abortion" as such would not be enough to startle those already going at it. The term "anti-abortion" is focused specifically on the target issue, instead of the widely-used marketing terms with which most people refer to their side of the debate; the fact that those terms are successful is, I think, due to the implied context of related ideas in them and continuous use by the persons and groups which first used and shared them.