Castro, who has not been seen in public since falling ill two years ago, said Angel Valodia Matos had been the victim of “mafia” tactics.
Matos and his coach were both expelled from all international competitions on Saturday, after the athlete kicked the referee in the head when he was disqualified in a match at the Beijing Games.
Matos hit out at Swedish referee Chakir Chelbat as soon as he was sent off for taking too much injury time in the middle of a +80kg bronze medal bout.
But Castro called for the athlete to be reinstated and denounced what he termed “the mafia” in the sport.
“Nothing can make me remain silent against the mafia. They have managed to play with the rules of the Olympic committee,” claimed the 82-year-old Castro.
“Appalled by a decision which seemed to him totally unjust, he protested and kicked the referee. His own coach had been the subject of attempted corruption … he was outraged, he couldn’t hold back,” said Castro.
Castro called for “total solidarity” with the athlete and the coach.
But Cuban Olympic bosses have not been so indulgent with Matos. While stating that he was the victim of an injustice they denounced the “serious breach of ethics” committed by the athlete.