Most “pro-aborts” are “had-aborts” seeking to justify their decision.
No doubt.
I don't think that's true (considering that less than 50% of the population would be biologically capable of having an abortion), but it would likely be true if you extended it to those seeking to justify the behavior of friends or loved ones. What conservatives need to do is directly challenge the notion that a wrong thing will cease to be wrong if enough people do it. Many people know that abortion is wrong, but think that if it can somehow become "not wrong", then they or their loved ones will be "okay". The message such people need is that it's possible for someone who has done something bad to become a good person, but the first step is to stop trying to pretend that what they did wasn't bad. There's no need to invoke religion. Even from a secular psychological standpoint, if one knows one did something wrong, the only way to free oneself of guilt is to confront the fact that one did something wrong--painful as that might be.
I wonder how liberals would react if some of the "had-aborts" started wearing shirts that said "I regret my abortion"? I can't think of any possible answer liberals could effectively put forth against that message.