How is a dirham of usury worse than a man committing adultery with his mother?

This Hadith (definition), "Usury has seventy-three doors, the easiest of which is like a man marrying his mother, and the worst usury is violating the honor of a Muslim man," was narrated with different wordings, but it is a rejected (munkar) Hadith and not authentically attributed to the Prophet, peace and blessings be upon him. Firstly, all its chains of narration and transmissions revolve around weak or abandoned narrators, or they are defective, and it has not been narrated with a sound chain. Secondly, its meaning is rejected and strange, for it is inconceivable that a dirham of usury is worse than thirty-six acts of fornication or committing adultery with one's mother, as fornication is one of the greatest sins and its corruption is immense. Thirdly, this Hadith was authentically narrated from two Jewish scholars, Abdullah ibn Salam and Ka'b al-Ahbar, which indicates that its origin is from the Isra'iliyyat (narrations from Jewish and Christian sources).