Also, note that I don't speed. But it's never a good thing for anyone to hog the left lane just because they're going the speed limit, or hog the left lane because they feel it's their job to be the enforcer of traffic laws. The rules of the German autobahn apply just as well to the US interstate or anywhere else. Move to the adjacent lane as soon as it's safe whenever you're impeding, or better yet, about to impede, the progress of another car on the passing lane. It's the correct thing to do in terms of safety and smooth flowing of traffic. Go ahead and report the speeder to the cops afterward if you want/can.
A car going above the speed limit causes far less aggravation on the highway than a left lane hog. A speeder is gone in a second or two, usually never to be a bother to the people they've passed ever again. A left lane hog, on the other hand, causes stress and frustration for minutes on end to anyone unlucky enough to be behind one. Go ahead and tell me which of the two is likely to be more of a hazard on the road.