Warnock had already been booked in the first half when he brought down Wolves striker Kevin Doyle to halt a threatening counter-attack.
But the England player escaped with a warning from referee Mark Halsey and rubbed salt into Wolves wounds by crossing for Emile Heskey to head the winner in a 2-1 success.
Look what I did: Aston Villa's Stephen Warnock celebrates setting up Emile Heskey's winning goal
It doomed Wolves to a third successive league defeat, while making it two wins out of two for new Villa boss Gerard Houllier.
McCarthy said: 'It was a great header by Heskey and we shouldn't take that away from him.
Final say: Emile Heskey heads in his 88th-minute winner for Aston Villa
'We could have done better when the ball came in - but I don't think Warnock should have been on the pitch.
'If it is a foul, it is a booking. Doyle has got Fletcher on the outside of him and it is a real attacking opportunity.
'It just rankles a bit. Had he (Warnock) not been booked already, I think he would have been.
'But I haven't spoken to the referee about it and have no intention to do so. I've welcomed him (Mark Halsey) back, and it's good to see him back in the game, but I won't be talking to him about it.'
McCarthy was also unhappy with the challenge by Villa substitute Steve Sidwell on Adlene Guedioura which resulted in the Wolves midfielder being carried off on a stretcher with a shin injury.
The former Republic Of Ireland boss said: 'We don't know how Adlene is yet. He went to hospital for an X-ray - but it doesn't look good.
'He tried to put his weight on it and let's hope it is bruised and nothing else. It was a poor tackle. It wasn't a nice tackle.'
Stewart Downing had given Villa a half-time lead but Wolves looked to have salvaged a point through Matt Jarvis before Heskey struck.
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