I remember when Idaho made the first limit in the mid to late 80's. Think it was that a hunting rifle should weigh less than 20 pounds. They were trying to keep hunters with 50 cal. rifles from shooting elk at extended ranges.
On the one hand, I'd agree and say that placing an arbitrary weight limit on hunting guns, most likely decided on by people who do *not* have any sort of interest, much less understanding of heavy guns and long range hunting, is a crock.
On the other hand, I can see a certain (twisted) logic to keeping the weight to a somewhat reasonable level: Most people (and I doubt many individuals here on this forum would qualify under 'most people') simply see a heavy gun as a means for either making a gun more accurate (i.e. less perceptible to wiggle etc.), or making it easier to shoot uber-magnums w/o having to practice as much and build up a recoil tolerance. Put the two together, and you have nitwits that sometimes I wonder if they know which end of the barrel is the dangerous end, shooting at live game at ranges they have no business doing so.
Regardless of the arguments anyone makes, the majority of the hunting public doesn't approve of people setting up a bench, and shooting an animal from across a field or canyon. I think a large part of it is because people tend to fear what they don't understand, but I think some of it is due in part to jealousy (there's really no way around it: it takes a minimum amount of $$$ in equipment and ammo to do it right, which most hunters either don't have or wouldn't spend if they could), as well as long range shooting of any kind tends to make it blatantly obvious real quick like if you actually understand what you are doing and can shoot or not... not something the average stump hunter wants rubbed in their face. That, and I'm sure most of the people who would approve or back such a regulation have either encountered, or heard tales of, one of the 'hunters' I mentioned above, that blaze away at long range, figuring that bullet energy makes up for bullet placement.
In the end, as much as I hate the idea of weight limits for hunting rifles, I think it's something that is going to happen, and not much that we can realistically expect to do about it. By all means, I'd love nothing more than to be proven wrong.