Playing the Devil's Advocate here (because this isn't my opinion at all): If you believed abortion was murder, as many if not all of the Pro-Lifers do, could you stand aside and not express your opinion? And taking it a step further, if you believed abortion was murder, honestly passionately believed that (potential) people were being murdered by the hundreds every day (or whatev the number is, I have no idea), would you not feel morally obligated to do something about it?
I understand the Pro-Lifers viewpoint. From what I have gathered, they believe abortion is murder... that it's just as bad as someone sticking a knife in someone, or blowing their brains out or whatever. In some cases, they believe it's worse than that because of the dehumanization of the potential person inside the womb. I just think it's the god damned silliest thing I've ever heard in my life, that a clump of cells = a human life. However, if I honestly, truly believed that myself, I think I would be aghast at the thought of abortions and likely reckon it with institutionalized murder.