If the allegations turn out to be gratuitous and unfounded, do you advocate trying the allegator so that the allegatee can recover damages to his reputation?
On the surface, that seems like a generally good idea. I'm not sure how it would work in practice, though. If there a hearing and a trial, the "allegator" (to use your word) will probably be the U.S. Marine Corps. And if there's a not guilty verdict it's hard to see how the USMC should pay damages if they acted in good faith.
I suspect you'd rather go after Murtha and other commentators who are talking about this case. As repugnant as we find these people, I don't see how anyone could legally go after them just for making comments.