If a person is going to freak, they're going to freak. I don't think we can do anything about that. Not everyone will freak though and I think if you're matter-of-fact about your explanation, don't lie but don't emphasize/elaborate it will or will not be all right? It is part of "you" and goes with your "package." :-) If someone cannot deal with that it is too bad but I don't think that person is someone one could ever be comfortable with unless they grow on their own. Let him bring them up if he notices/asks and see what his "mood" is when he asks, whether he's tentative or seems freaked or what not. If he seems merely curious/accepting tell him more than if he seems angry/freaked where I would shut down and say something like, "they're just old scars of mine" and change the subject, my physical position/focus abruptly.