Ferguson was banned for four games, two of them suspended, and fined £20,000 for comments about the fitness of Alan Wiley after October's draw with Sunderland.
He was also warned about his future conduct, but on Saturday labelled the dismissal of Darren Fletcher ridiculous and was also bemused after United's goal initially seemed set to be disallowed for offside.
The flag went up against Wayne Rooney, itself a marginal call, but the goal stood after it was established that Blues defender Scott Dann got the crucial touch.
Ferguson told ESPN: I've not seen a softer sending-off for a long time. It's absolutely ridiculous, really.
I've been watching Mark Clattenburg this season. He did the Arsenal-Tottenham game - you had to have someone hit with an axe before he'd book anyone in that game, and he sends a player off here.
There were some wonderful and weird decisions out there. The linesman gives offside for our goal - it's an own goal, and he gives offside! Anyway, we carry on.
The Reds had trailed to Cameron Jerome's opener late in a first half which Ferguson's men dominated, and the United boss continued: We played absolutely brilliantly in the first half and to lose a goal right on half-time was a sickener.
Birmingham are in real good form, they work so hard and make it difficult for you so we've got to be satisfied with a point, particularly as we've ended with 10 men.
Source: Manchester Evening News