[Cushman]

It’s not a shift in usage, it’s a term of art. Informally it could mean just crossing the line to enter the business, but unless you live in a turn-of-the-century company town, no one in the union is expecting anything related to that by default.

In labor, “respecting the picket line” is a moral action for union members (or scabs) which by definition couldn’t apply to a spontaneous self-directed consumer boycott.

Not to put to fine a point on it: if you show up to someone else’s labor action claiming solidarity, and then independently decide to pivot the action to a totally different set of economic incentives, you are — almost literally! — a scab.

[tptacek]

A scab is someone who works in violation of a strike. It's not a generic term for anybody disfavored by labor activists.

[Cushman]

Ouch! Fair cop since we’re nitpicking, but I was trying to be cute about that — the joke started out more like “you’re technically crossing the line to scab as a strikebreaker”. I’m aware that it still doesn’t make sense unless there’s a sympathy action by the strikebreakers’ union, unfunny and unhelpful in the first place, thanks for the correction :)

Edit: Ah shoot not again. What I meant to say was “scabbing as an agent provocateur”. Sorry, I’ll quit while I’m ahead!