Micha:

I have never heard it claimed that the terms “hard-working” and “law-abiding” are Southern strategy code words,

They are. They’re especially closely associated with Nixon- and Reagan-era efforts to pull in working-class, often unionized white men (“hardhats,” “Reagan Democrats,” et al.) for the Southern Strategists’ racially-charged anti-welfare and Law-n-Order kicks.

Try thinking about it in reverse, if that helps. “Hard-working” and “law-abiding” are deliberate contrast terms for “lazy,” “shiftless,” and “criminal.” These terms were all deployed with pretty clear racial dimensions during the political debates in question.

(Personally, I’m all for an anti-welfare kick; but the Law-n-Order kick has been one of the single most politically toxic positions in mainstream American politics for the past several decades. And in either case the deliberate use of racial resentments for political ends is a nasty business.)