I just put a bit more credence in NRTLC's assessment of Fred's pro-life positions than I do some actor's.
It depends what you mean by credibility. NRLC is a political organization, and makes endorsements based on political considerations. They obviously believe Fred Thompson is their best choice to get someone elected who will move the ball forward on pro-life issues.
I’ve seen the state affiliate of NRLC endorse a democrat who was less pro-life over a strong pro-life republican because the democrat was an incumbent, even though his election gave the democrats the senate, which effectively killed any chance to pass pro-life legislation. In fact, the DPV ran anti-pro-life advertisements against the democrat, while the democrat touted his endorsement by the pro-life group.
But my point wasn’t about who is more credible, it was simply that it is bad when you get an endorsement from a close friend and in that endorsement he says he doesn’t think you will accomplish what he wants on his major issue.