The DMCA, or like in this article's "engineering" case, outlaws the whole act of thinking. Some areas are just off limit, no matter what you think, Sun rotates around the Earth or Earth around Sun.
In certain highly restricted domains (typically embedded systems), liability for bugs becomes somewhat more realistic.
That, divorced from further arguments, is not an extraordinarily strong argument against liability for defects. After all: the engineer who builds upon such a stack has presumably, more or less consciously, made the decision that defects are acceptable - otherwise they would have chosen something less complex. Is there any particular reason someone should not be held accountable for that decision?
You don't get to blame civil engineers for structure failure if the steel provided had material faults (that couldn't be detected by said engineers exercising due diligence).