The "God-given" part of that quote is crap, of course. And the rest of it is, admittedly a crass thing to say out loud. But isn't it implicit in the establishment of the 2nd amendment that the founding fathers knew the basic context to be true? Certainly, they had to have understood that assassinations and gun crimes were an inevitable consequence of 2A, and thus a price to pay for the "right to bear arms".
Not at all.
The idea that the 2nd ammendment would grant people a right to bear self-loading firearms with rifled barrels, while acting independently of any kind of well regulated militia, is not something they could have considered, as the founding fathers were not, to my knowledge, gifted with the psychic powers necessary to predict two centuries of innovation in firearms design, and of political and social change.
Assassination and gun crime using the weapons and tactics available in 1789, and within the social structures and norms of that time, were absolutely nothing like they are today, and absolutely could not have been understood by the people of that time.
As I have said before:
To be honest, the "mindset of the founders" is not something that should have ANY influence on what we do today. They lived in a completely different world. One where personal arms were muzzle loading long guns and pistols with very low effective ranges and very low rates of fire; And where a nation could consider, as a reasonable option, having no standing army at all. They also lived in a time when the success of their revolt was far from assured in the long term, and there was a very real threat that the British might re-take the American colonies.
They sure as shit didn't imagine that the Bill of Rights might be used as some kind of 'holy writ', perfect and immutable - they expected that the constitution would change a LOT over time, because they were not stupid enough to think that times were unchanging.
And they certainly didn't intend their rules to apply to the question of whether people could carry self loading rifles with large capacity magazines without having any responsibility to submit to military discipline if called upon to serve.
The second amendment provides that citizens have the right to own guns in order to ensure that they are suitably equipped and trained if called upon to serve their nation. It assumes a responsibility for those who own guns to turn up at well regulated training sessions, and to obey the regulations imposed by the state militias. In short, in today's USA, it gives every citizen the right to bear arms as a part of the National Guard for his state. All further interpretation is revisionist nonsense.
But nobody cares what it says, or even what it means. It's a political toy, and you would be better off ditching it altogether. But you can't, because your nation is dominated by morons who fervently believe that 'ancient wisdom written long ago' is a route to knowledge.
If the founding fathers were confronted by the (very uncommon) case of a person going crazy with a gun, they would expect the citizens to simply overwhelm him once he had fired his weapon - because having done so, he effectively disarmed himself, and was left in a revealing cloud of gunsmoke (no hiding for snipers in those days), not very far from his target (before the invention of the Minié ball, even a rifle had a very short effective range against a man-sized target), with an empty gun.
Sustained gunfire in 1789 was possible ONLY from a well trained and disciplined
body of men (a "well ordered militia", if you would), who could fire in turn, and reload while others were firing.
You could use a pistol of that era in an assassination, but you would need to get very close to your victim, and would probably be more effective with a knife.
The founding fathers thought that the consequence of the 2nd ammendment would be a nation that could defend itself from the British, and from the Native Americans, and from slave revolts, without the expense of paying a standing army.
Crazy people shooting other white citizens wasn't their idea of "well regulated", and wasn't a practical option even for the craziest of their countrymen, with the arms then available.