Nevertheless, saying that poor and abused people use knives and not-poor white men (implicitly, by way of being contra to the former) use guns is a sub-optimal and vaguely racist way to structure that sentiment.

I don't disagree, but I think maybe we interpreted his comment differently, as the way I read it was the other person making exactly this point. I took his comment to be explaining from the perspective of one imposing such a law, as opposed to a belief they're presenting as their own.

Even more complex when you add in the shifting terrain and definition of "whiteness" during the 20th century, e.g. Irish-, Italian-, Jewish-Americans et al., especially in the context of early and mid-20th century weapon regulations.

Yup! A couple other examples I can think of are stilettos and switchblades being banned shortly after Italian knife makers picked up on the trend, under the guise of being "mafia" weapons. One excuse they often go for is that the blade can be deployed too quickly, which is BS; you can give a 10-year old kid any old folding knife with thumbstuds, and with 5 minutes of practice they can deploy it just as quickly as any spring-loaded knife.

It's a tale as old as time. Any time the feds see a group of people arming themselves, and they're not white (or not white enough), they'll bend over backwards coming up with any justification to strip them of their defenses.