This is Logically Known as a Non Sequitur
The logic behind that leaves my head smoking like Nomad just before Scotty beamed it off the Enterprise.
Publicola put it well: “Personally I would have thought, ‘Since my unarmed son was stabbed with a knife then obviously he wouldn’t have been stabbed if he had a gun. So therefore I will encourage people to learn how to use & carry guns so they won’t be stabbed to death by criminals the way my son was.’ But that’s just me.”
Me, too. (But her son didn’t die. He recovered.)