Maybe if the entire right wing didn't distort the issue into a giant Straw Man = 'Banning guns', a conversation could ensue. It's entirely easy to point to a law or regulation that no one is suggesting and conclude that it won't work. What no one on the right seems to be able to admit is that reasonable regulation (licensing, registration, background checks, insurance requirements, taxes on ammunition) reduces the risk to the overall population - and that that end is desirable. We don't have to prevent las vegas perfectly. And maybe 'assault weapon' is difficult to define precisely. But how can anyone deny that imposing some purchasing restrictions on weapons designed to primarily kill humans would have saved some of the lives in this disaster?
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Calling them reasonable doesn't make it so.
Licensing: I'm fine with this but I have yet to see any proposals in this regard.
Registration: A list of guns--the current holy grail of the gun banners. It's not going to do anything about the criminals, it's just a list of the law-abiding. It will do very little for safety but it will make future confiscation a lot easier.
Background checks: Be
reasonable about this and it will pass in most places. The problem is that the left is no more capable of coming up with reasonable gun rules than the right is at coming up with reasonable abortion rules. However, I think the whole idea is wrong--if you have licenses you don't need background checks on purchase.
(How about a compromise? You can get a gun license {which involves a background check}
or you can have a background check on transfer. That's close to how it worked here--there was no gun license per se, but you could show a CCW permit and avoid a background check. The ballot measure we just had on background checks would have gotten rid of this exemption had it not been a piece of crap that was impossible to actually implement.)
Insurance: Guns are involved in very few incidents for which insurance would apply. If you're shooting at a person it's either self defense (at which point the person you shot has no basis for a claim) or it's criminal (and insurance always excludes willful criminal acts.) The requirement to have liability insurance on a gun is really just an attempt to drive up the cost and to get a backdoor list of everyone's guns.
Tax on ammunition: Crap. The people that use a lot of ammunition are very unlikely to be using it in a way that imposes any costs on society.
As for a weapon primarily designed to kill humans--about all I can think of along those lines are specialty weapons for spies and special forces. No other weapon has a primary purpose of killing.
Take your "assault rifle": The primary purpose to which these are put is shooting at targets. Even in a self-defense situation a gun is unlikely to be fired--the primary purpose is deterrence. (Which is also the primary purpose of all ordinary military weapons. We don't build them to shoot them, we build them to discourage other countries from doing things that put us in a position of needing to shoot them. They're only fired if the primary mission fails.)