And I suspect very strongly that the engineers on this particular project would have clearly violated any standards of professional ethics we could agree on.
Civil war amongst software developers, with utter lack of due process, and ostracism as punishment are not as pleasant to the ear as "consensus," but that's the end result of what you're proposing.
This, of course, misses the central flaw in the proposal: If "good" companies refuse to hire engineers with work history at "bad" companies, you'd be forcing the very engineers who now want to do work you consider "good" back into doing work you consider "bad."
Setting aside the horrific personal implications this ham-fisted approach would have, by its very nature, a refusal to hire policy would have the exact opposite effect that you intend.