Ferdinand was given a three-match ban for swinging an arm at Hull's Craig Fagan in an off-the-ball incident on Saturday, and the suspension was increased by a further game as The FA said the player's decision to contest the charge was "frivolous".
The ban means Ferdinand is unavailable for the upcoming Premier League games against Arsenal, Portsmouth, Aston Villa and Everton, but Ferguson feels the FA is giving off conflicting signals in the way they handle disciplinary cases.
"We have to decide whether to appeal because there are conflicting ways in which these decisions are being viewed," he said. "I watched the game between Leyton Orient and Charlton on Monday and there was an elbow on the Charlton player three times as he was running with the ball.
"But nothing has happened with that. There is a lot of confusion there, although we accept that for tomorrow, Rio is banned."
Meanwhile, Ferguson has called on United's travelling fans to refrain from abusing Arsene Wenger when they head to Arsenal on Sunday.
Wenger has repeatedly been the subject of particularly offensive chants from opposing supporters during his time in England and Ferguson feels it must be stopped.
"I know there has been some terrible abuse from our fans towards Arsene Wenger," he said, "but a line has to be drawn. They must know that themselves.
"It is unavoidable that managers do get abused. I get it myself. Most managers do. Sometimes I can't hear these chants or make them out, but it has to be controlled."