I think you’re missing the point. Bringing in difficult to obtain weapons as part of the conversation muddies the conversation about controlling the currently ubiquitous weapons being used.
As an analogy, let’s say someone blows something up and hurts people, using dynamite or homemade explosive using gun powder:
“Anyone who has access to the dynamite and RPGs and C-4 should be held responsible for what’s done with it!”
“Wait, there was an RPG or C4? I’m pretty sure outside the military it’s pretty difficult to get ahold of either of those. They’re already heavily regulated.”
“What difference does it make? They’re explosives used to blow things up and kill people.”
“Right, but, again, those are heavily regulated, while what happened was with dynamite, which is not.”
“OH! So it’s OKAY since the dynamite is not as regulated!”
“No, it’s just a different conversation about RPGs and C4.”
“Only if you have an agenda!”
Vs.
“Anyone who purchases dynamite should be responsible for what happens to it, unless they can show they’ve properly secured it and didn’t give access to it to someone they shouldn’t.”
“Agreed, dynamite and gunpowder explosives are common and not as regulated as they should be.”