<< If people have the right to break the law by speeding, don't I have the right to drive the speed limit? >>
If you want to forget about law technicalities for a moment, wouldn't it make a whole lot of sense for people to drive in the lane that suits their speed? If you are in a leftside lane and there are cars behind you (presumably tailgating), then why not move into a rightside lane?
I think there's a lot of ego at work. You've got peeps who don't want to move because they are following the letter of the law and you've got peeps who don't want to give in because they are following the natural flow of the road. The two clash and boom! aggressive driving, road rage, whatever.
That's why I advocate drivers to quit worrying about speed signage all the time and instead worry about making sure their car's perimeter is reasonably safe from other cars. It is a bit safer to speed up temporarily in order to move into a rightside side than it is to have somebody tailgate you all the way. The tailgater will not quit, that is not in their nature. So just move out of the way. It may not be "morally ideal", but it will take the lid off any steaming pots.