I don't see what the big deal is with having more restrictive gun laws. Even though their reference in the 2nd amendment has to do with protection from a tyrannical government (which wouldn't really work in the US today, as +Mike Mac
explained), we accept them today mostly for hunting and defending ourselves. Arguably, another use is for target practice (for sport/fun), but you can't really say what a valid weapon is based on this because it's too vague.
For hunting, there's no need for the ability to shoot more than a few rounds quickly before animals scatter and you need to blend in again. Defending yourself shouldn't require more than either a shotgun or a pistol. If you really need an AR-15 to defend yourself then you should probably stop pissing off the mafia and go into witness protection or something.
Restrictions can be done gradually too (less economic impact) . For i stance, give manufacturers a year or so to stop making newly outlawed guns, another year or two to stop selling them, and then wait a generation for the ridiculous numbers of guns floating around to die down. Nobody (well almost nobody) is advocating that the police come to your house and take your guns. I suppose if you got caught driving with them and weren't relocating / moving, then they'd take it away.
Guns' primary purpose is to kill. There are accepted reasons for this, but we need to balance them with the unacceptable ones. Sure it's people that kill people, but it would be a whole lot harder and more expensive to try and accurately
predict who will do it than just keeping a closer eye on the tool of choice.
I disagree with the argument that this leads to a slippery slope of the US effectively regressing to something like a Soviet Russia. That may have been a valid concern just a few decades ago but technology has allowed the relatively small difference in time lead to significant protection. Everything the government does is almost instantly broadcast around the world in HD. There is also much more of a global community than there used to be, of people and governments. Plus if they really wanted to control us, they have much better weapons than we're arguing about.
Ideally, I think we should start out with what valid uses of guns are, define limitations of what characteristics they can have for ordinary citizens (power, size, rounds, delay between rounds), and say everything else is for killing on an unacceptable scale. That is of course ideally and in reality we'll probably just ban some guns with little effect. There are so many floating around out there only drastic actions that violate people's rights would get short term results. We just have to draw a line in the sand (it really shouldn't be that hard to agree on where) and help them slowly fade away.