The winger, perhaps still feeling a sense of injustice when he was denied a penalty earlier, reacted angrily to a foul from Henri Lansbury by elbowing him in the stomach five minutes before the break.
The incident occurred right under referee David Webb's nose and he did not hesitate when issuing the red card to leave McCarthy fuming at Martin's naivety.
"It's always the one who retaliates and you get caught," the Town boss said.
"Whatever he's done, he deserved it because he threw an elbow."
Ipswich's misery was compounded when Richard Stearman was also dismissed for a second yellow card with over 20 minutes to go and Forest eventually made their numerical advantage count thanks to Lewis McGugan's late winner.
When asked whether he would speak to Martin about his conduct, McCarthy added: "I'm not going to stand and have a long-winded chat about it.
"It's cost us the game - one was bad enough, the second one's just cost us.
"Of course I'm going to be having a discussion (with Martin) but I won't be telling you what I've said."