You have to make the case for owning them, not for sport or hunting, but self-defense and defense against tyranny.
The sad part is that while true, these arguments make little ground among the unconvinced, and none at all with the anti-gun bigots.
The simple truth, recognized but never admitted to, is that the ant-gun people
are the tyranny that we must guard against.
Both in and out of government. Matters not if their paycheck comes from tax dollars, or Bloomberg or Soros, it is their actions and words that matter.
Just because they don't wear swastika armbands doesn't mean they aren't tyranny.
As to personal protection, many don't recognize that as a right, or that using a gun to do it is a valid option. They believe we should not do it, that is what the police are for. And even the ones that do admit that while we shouldn't have to, we do need to use guns for protection sometimes, they argue that weapons like the AR are neither useful, nor suitable for self defense, and therefore should be banned.
If you want to argue over the effect of violent video games, fine, but don't stop there. Recognize that it isn't just video games, its everything on a screen 24/7.
Don't just look at games, look at everything seen on a screen, in home, in theaters, and today in your pocket and your car. Realize that on a subconscious level (and sometimes a conscious level) our "entertainment" are training films.
The generations in the 1930s and 40s didn't have tv. They had radios, and those well off enough, might go to the movies, once a week, or so. By the 50s and 60s, TV got into many, then most homes, and it ran from around 6am to midnight, and was shut down the rest of the time. In the 70s, and on up, we got TV that never went off the air (cable, at first, now satellite, as well),
Combine that with general greed, and the constant need to go "further" in nearly every aspect, but especially in violence, in order to attract viewers, and we have gotten past just realistic looking violence and into unrealistic fantasy graphic violence. And the public eats it up. People don't just fall down when shot in the movies today, they "splatter".
One doesn't need any study to recognize that with many things, the more you are exposed to something, the more tolerant of it you become.
Back ages ago, about the time we started getting 24/7 tv, someone did a "study", sorry I don't remember who or exactly when, I do remember one of the points they claimed was that the average American child had witnessed some 17,000 (seventeen thousand) murders on TV by the time they were 18. And the point was brought up pondering how this could possibly be a good thing for our society...
Now, today with our 24/7 entertainment cycle (and I include the "news" in that) and video games, I'm confident the number of murders witnessed (and performed in games) is much higher.
Yes, there are many other factors involved, I'm not discounting them, just not addressing them here. Just want to make the point that we have been "training" a couple of generations subtly (and sometimes not so subtly), via the TV & movie screen, and that has to have had an effect.