I should say right off that I support your view on 'Avg. Joe's' w/o training trying to be 'Heroes' intervening in a real mass shooting...only adds to the carnage.
Let me also take a moment to reframe the whole question of citizen gun ownership (I promise to get back to your specific questions)...you may recognize some of my points if you've read through the previous posts...
>There should only be three reasons for a citizen to own a gun...1) Home Defense...2) Hunting...and 3) Sport (Target) Shooting. All other uses are reserved for authorized Police and the Military.
>None of those uses requires large magazines or high rates of fire...a 9mm pistol with 10 rounds should be sufficient for #1...a single shot (or low volume storage) 30-06 for #2...and a .22 long rifle
for #3.
>any weapon with capabilities beyond these is unnecessary and only diminishes community safety.
Now, as to your questions/comments...
>As I've said before, I use the term "AR-15" in an 'exemplary fashion...like an 'Avatar'..but to address your questions straight on, after a little research, the "AR" designation stems from the name of the firm that originally designed it (ArmaLite) back in the late 1950s...again, that specific weapon isn't the issue...it's the 'genre'...more on that to follow.
>You ask about homicides by other means (stabbings, beatings, strangulations, etc.), but don't say why...so I'll have to make my own assumption...It's my guess that you are asserting that 'Assault Rifles' aren't the only means of causing homicides, so why single them out...Everyone acknowledges the fact that there are sadly a wide range of homicidal methods, but when it comes to "Mass Murders, i.e. 10, 20, 30, or more at a time, then those perpetrators have already cast their ballots by choosing Assault Rifles...this is what raises attention and concern for them specifically.
>Q: "Who decides...on magazine size, etc."?...Answer: Congress; States; Municipalities in consultation with numerous knowledgable sources. Note that Justice Scalia wrote an opinion on the 2nd Amendment that included the phrase "Like most rights, the right secured by the Second Amendment is not unlimited. [It is] not a right to keep and carry any weapon whatsoever in any manner whatsoever and for whatever purpose."...several decisions by Appellate Courts have upheld the right of various levels of government to ban certain guns and gun related products.
>C: Open carry or conceal and carry are among the safest states...Reply: First re-visit my opening remarks on the justifiable uses of guns, but add to that my reference to your own admonition of 'Avg.Joe's' walking around in anticipation of using those weapons as 'Heroes'...the more guns that are carried only increases the odds of clueless users creating more loss of life...
Some folks say that 'Law Abiding' "Good Guys" will save us from danger, but if everyone in the population who doesn't have a police record carries a gun, then simple statistics predict we'll have more fatal encounters like the retired Police Captain in Florida I mentioned in an earlier post...shot a man dead in front of his wife in a movie theater because he wouldn't stop using his cell phone (to text his babysitter)...before the shooting everyone would have lauded him as the quintessential "Good Guy" who should be carrying a gun in public. A rarity?...sure, but think of all the un-diagnosed gun owners having a "Bad Day" because their boss just fired them, or their wife left them, and they've been binging on "Call of Duty"...I'm sure you get the picture.
>Q: How many were killed by mostly peaceful protesters last Spring and summer and where was the outrage?"...Reply: Somewhere around 25 people died in protest related shootings, but from my very quick research, the majority were not perpetrated by protesters, but rather 'outsiders' (e.g. Kyle Rittenhouse carrying around his AR-15)...as to the 'outrage', the protests themselves were an expression of outrage for repeated killings of blacks...which some people thought was "unnecessary"...each of those victims family members and friends experienced heart-wrenching loss that an absence of guns outside the home could very well have prevented.
Finally (for now), let me say that the worldwide data on gun deaths is clear...countries with strong gun laws have very low 'body counts'...that's a fact...as Justice Scalia said, the 2nd Amendment is NOT (my emphasis) unlimited...we've already had a temporary ban on assault rifles (without an 'uprising')...Australia banned assault rifles, saw a major drop in gun deaths, and didn't have an uprising. The majority of ALL Americans supports stronger gun laws, and even 25% of NRA members support a ban on assault rifles.
While there are many more things to discuss on this topic, I'd ask you, if you choose to reply, focus first on the "3 Uses" position I put forward and then acknowledge Justice Scalia's statement on the 2nd Amendment (it was for the "Majority" by the way)...