Stuart G actually hit upon a good point (And one the Left often conveniently ignores when discussing this issue) in the last couple sentences of his op: A MAJOR part of the reason for our society's current problems with gun violence is from our culture glorifying gun violence.
Between much of pop culture portraying gun violence as cool, such as the innumerable gangsta (c)rap music videos showing gangbangers blowing each other away while looking like heroes and role models in the process, and the widespread media who leap at any opportunity to exploit tragedies for ratings ensuring almost- instant global fame to mass shooters, it's a culture that quickly corrupts people.
THAT'S what I'd imagine the Founding Fathers would take issue with. They knew their new nation needed a strong moral compass in order to survive, and would thus be enraged at how much our current culture makes rampant violence, lawlessness, and general evil look cool.
