The Wigan manager has lashed out at the referee after the game at the Stadium of Light took a turn for the worst for the Latics as Jordi Gomez received a debatable red card
Gomez was sent off early in the second half following an over-zealous tackle on Sunderland left-back Danny Rose that led Webb to brandish a red card.
Martinez told reporters: "I think it's harsh. It's harsh because Danny Rose loses the ball slightly. Jordi tackles as a striker tackles, showing the studs, but he never leaves the ground, it's not a two-footed challenge.
"I can understand why the referee gave it, but I think it's very, very harsh. My disappointment is that [Sebastian] Larsson has made a worse tackle against [Arouna] Kone and is not even shown a yellow card.
"That's just as you want as a manager, you want consistency for both teams. It's down to the referee's decision if he considers that that challenge is a red card, but then every challenge in the same manner should be a red card.
"That's the disappointment. At the moment, we are on the back of a few bad decisions and you just need to take it in football. It happens.
"You just hope that over the course of the season, you are going to get good calls coming in our favour even though now, we find it difficult to understand that's going to happen."
Wigan have four points from a possible 18 and sit 16th in the Premier League. Their next fixture sees them host in-form Everton next weekend.