But, scarce observed, the knowing and the bold Fall in the gen'ral massacre of gold; Wide-wasting pest! that rages unconfin'd, And crowds with crimes the records of mankind For gold his sword the hireling ruffian draws, For gold the hireling judge distorts the laws; Wealth heap'd on wealth, nor truth, nor safety buys, The dangers gather as the treasures rise.
Here the speaker gets into talking about that gold stuff: loot, cheddar, dollar dollar bills y'all, money. He says that everyone is corrupted by the desire for money. Using another metaphor, the speaker likens money to "a pest" that takes over human society and leads to many crimes.
People hire themselves out and commit crimes for money. Judges twist the law for money. The speaker also says that no matter how rich we are, we can't buy truth or safety. On the contrary: more wealth brings with it more danger.