One should consider that Vidura was inferior because of being lesser than Dhrtarastra and others. Dharma-raja, Yama, was born as a sudra by the curse of Mandavya in the form of Vidura. Who would carry out punishment while Yama had the sudra body? Aryama held the post. Abibhrat is poetic license for abibhah. One time the soldiers of a king were chasing some thieves. They caught them near Mandavya who was performing penance. Tying him up along with the thieves they brought him to the king. By the king’s order, they were all impaled. But the king recognized the sage, and had him taken down, and took care of him. The sage went to Yama and in anger spoke. “Why was I impaled?” Yama replied, “As a boy you pierced a grasshopper with the tip of a kusa grass, as play.” Hearing this Mandavya cursed Yama, “Since you punished so severely though I was an ignorant boy at the time, you should become a sudra.”