I accept your concession of the point.
When you think you can demonstrate the necessity for background checks, let us know.
I didn't make a concession you just keep insisting you made a point.
Was Ator able to buy a gun and circumvent the background check system even though legally he was not allowed to possess one? Yes or no.
The man was a violent sociopath who must have known he was going to die when he went on his shooting spree, so are you seriously arguing he would have hesitated to buy a gun illegally if he couldn't have bought it legally?
A good reason to have all guns registered, and tracked from manufacturer to end buyer. The end buyer is responsible for the gun an any untoward act, including murder; if the gun is lost, sold or otherwise disposed of, and the weapon(s) is not reported to the ATF&E Agency (or other data base established by law), the end buyer should lose his or her 2nd A. Rights.
There is no way to keep track of guns sold illegally. If the original buyer bought the gun illegally, it will forever be impossible to track. If a gun is stolen, it will do you no good to have the registration. More gun laws will not deter crazies like Ator of determined gang members, drug dealers or other criminals or crazies who believe they need guns from acquiring them illegally. This whole issue is political bullshit. According to Wikipedia, there have been 297 mass shootings in the US so far this year, yet the media only tells us about a few of them and all the arguments about more gun laws are based on only a few incidents and a few personalities of shooters. While the body count rages in Chicago and Baltimore, Democratic cities, the Democrats only want to talk about a single shooter in Texas, a Republican state. The mayor of Chicago says it's not my fault people are being killed in such high numbers on teh streets of my city; blame the Republicans in states without gun laws I approve of and ot the fact that I demonize the Chicago police so that they no longer want to go into high crime areas.
~ARGUMENT: This is not a valid argument (hence: ~argument).
It assumes gun registration is not practical, but not a proof of that conclusion. If we want to mitigate getting guns out of the hands of the few, then the many will follow a law which requires guns in the public domain to be registered in a data base.
Any gun in the possession of any person without a serial number, or with a serial number and not registered (some guns before 1968 might not have a serial number, so that's a problem to be solved) needs to be surrendered. They may buy back their property if they provide evidence of their residence, register the gun, and pass a background check.