Wrong. The murderers were never prosecuted for their crimes. Instead their accomplices were. Abortion became common when a significant percentage of the population came to believe that it was "a women's right."
Wrong about what?
You asked how to counter Lallier's objections. Lallier's "Pandora's Box" example spoke exclusively about these accomplices. Not the abortionists. That is the very example refuted by historical example.
Are you claiming this is an invalid counter-argument because it doesn't speak to the abortionists themselves? How does that have anything to do with countering Lallier, who doesn't mention them?