Speaking before Saturday's clash with Liverpool at Old Trafford, their first league meeting since Liverpool's Uruguayan striker Luis Suarez served an eight match ban for racially abusing United defender Patrice Evra at Anfield in October, Ferguson told CNN:
"I don't understand at all where its coming from.
"This is a moment where we have to take stock and we should do something about it, if it's surfacing again, and be really hard and firm on any form or shape of racism.
"There have been a couple of examples recently which is not good. In 2012 you can't believe it. It was obvious maybe 20 years ago and the improvements have been there for everyone to see."
Suarez missed the FA Cup win over United on January 28 while still banned but he returned to the Liverpool side as a substitute against Tottenham Hotspur on Monday and is likely to play at United at the weekend.
Chelsea skipper John Terry is awaiting trial in July after being charged with racially abusing Queens Park Rangers defender Anton Ferdinand, which Terry denies.
However, he was stripped of the England captaincy last week by the English FA, who ruled he could not lead the England team until the trial was over.
