I wouldn't dare to suggest anything honestly as I wouldn't want to possibly make matters worse. You'd need some very very fine grit polishing material to prevent matting the mirror-like finish, and there's always the risk of leaving some kind of uneven finish that looks different depending on how light falls on it. Plus you'd want to avoid abrading the surrounding anodized aluminium and so on... Seems a risky operation, honestly.
May I suggest you just live with it? See it as patina, and next time you go through airport security maybe keep your laptop in a sleeve. (Which reminds me, I should buy a sleeve for my laptop, for if I need to travel with it. Thanks for the tip, man!

Or well, for taking one for the team and find out that airport screening machines aren't safe for macbooks...)
There's always the "buy an entirely new display assembly" nuclear option of course, at like what, $1200 cost or something? Seems a bit excessive maybe. *shrug*