McCarthy said he made the changes to protect his players from injury but was criticised by some Wolves fans who had made the trip to Old Trafford and subsequently asked to explain his selection by the Premier League.
He was also roundly criticised in some sections of the media, but McCarthy hit back after seeing his team beat Burnley at Molineux.
"I have to say that there have been one or two dubious characters who have been giving me a bit of stick," he said.
"They have questioned my honesty and integrity when I think I stand up for all those things."
Asked if the victory over Burnley - a result that lifted Wolves out of the relegation zone and up to 12th in the table - justified his team selection for the game at Old Trafford, McCarthy was unequivocal in his response.
"I'm not looking for vindication by it, I'm looking for points," he said.
"I'm delighted I have players that believe and trust in me to make the right decisions and then perform like that.
"We've had nine points out of 12 since the Birmingham game, and people who were here when we played Birmingham would never have thought that. It is about all the games, not just about today."
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