A man threw ink on Sahara chief Subrata Roy, who was being produced in the Supreme Court on Tuesday after his arrest last week.
After the incident, the accused claimed to be a lawyer Manoj Sharma was beaten by the lawyers and was later detained by the police.
"I fight against the people who dupe the common man of his saving. He (Roy) is a thief of the poor," said Sharma.
Roy was brought to Delhi on Monday night after an overnight halt in Agra.
The order to arrest Roy was issued on February 26 after he failed to appear in connection with a case in which his company was directed to return Rs. 20,000 crore to investors.
Roy surrendered last Friday and was arrested by the Uttar Pradesh Police.
He was lodged in a guest house of the state forest department at Kukrail in Lucknow after a local court directed the state police to keep him in its custody till March 4.