So two things
While polishing glass is possible (I've seen kits), it might be a more aggressive procedure than the mirror can tolerate (think fairly heavy mechanical action on the fragile internals of the mirror assembly itself).
BUT, aren't our mirrors actually a plastic material?
If that's the case, then it might be more viable (plastic being easier to polish than glass), but still, you're going to be rubbing the hell out of the internals... Back and forth, back and forth, up and down, up and down...
(Easy now... We're talking about polishing something.)