Lazio Football Club historian Alfonso Dessi has described Paolo Di Canio as a "true fascist" who had a "huge impact" on hooligan supporters because of his political ideas.
Dessi told ITV News that Di Canio's political views do not affect his football, but revealed his "bad temper" often got him into confrontation with Lazio's board.
Di Canio was confirmed as Sunderland manager yesterday amid a row over his political beliefs.
As a player, he had two spells with Lazio and is widely revered as a hero for the Rome-based team.
Sunderland manager Paolo Di Canio denied he was a racist or fascist after his controversial appointment received fresh criticism.
Yesterday's press conference at Sunderland's Academy of Light training base was illuminating in every way but one.
Paolo Di Canio refused to answer questions on whether he is a fascist but said the controversy surrounding his appointment was "ridiculous."