Point taken...but still, blame the villain, not the tool...
No disagreement with those sentiments ... but my take on it is likely just a bit different than yours.
The individuals that perpetrate these atrocities are certainly responsible for their actions in doing so. On that we agree.
On the other hand, to ignore totally the devices that they use to accomplish their evil acts would be wish-casting at best ... if not borderline delusional. Such devices are part of the scene ... and will be part of the conversation.
The regulation of explosive materials (dynamite, C4, etc.) in the US is something one sees very little public outcry over. That's probably because the destructive potential and misuse of such things is readily apparent to a majority of general public.
Large capacity mags, bump stocks, and semi-auto weapons are similar - in that they also have a high destructive potential and can be similarly misused.
The question will be what to do about it.
That is where the conversation will occur.
I would be remiss if I failed to note that all of the above items have legitimate uses - regardless of whether those uses are vital (protection of oneself and others) or trivial (personal enjoyment, sporting)
And on the matter of
regulation of semi-auto firearms, I'm not so sure that it would be "a violation of the Second Amendment" ...
Was that holding or decision by SCOTUS where it was found to be so ?
I know they never reached the merits on the previous assault weapons ban.