Same concept as blood money. To be dramatic, if the wrench was made with ore from a mine where your father worked, and he was killed and the ore was stolen, would you do business with the company that hired the mercenaries that killed him? Would you buy a wrench from them? if one fell into your hands, would you use it? It's just a wrench, after all, but you can see why somebody might have strong feelings about it, even if you ultimately disagree with them.