Sorry, but this was a painful read filled with failures of logic and uniformed opinion.
The track-record shows that insane killers that perform mass shooting incidents almost always per-meditate and consciously choose their venues. The CO theater shooter, for example, skipped overqualified 5 more convenient theaters to get to one with a no weapons policy posted. He wore body armor. He was deliberately acting to lower his chances of being threatened by armed resistance.
Then there's the idea that violent crimes are stopped only by shooting the assailant. Statistically, most criminal incidents stopped by a firearm end when the crimal has a gun pointed at him. He surrenders or flees. He doesn't get into a shoot out.