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.
McCarthy said: "It was a great header by Heskey and we shouldn't take that away from him. 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."
Stewart Downing gave Villa a half-time lead but Wolves looked to have salvaged a point through Matt Jarvis before Heskey struck.
McCarthy continued: "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."
Houllier revealed his faith in Villa matchwinner Heskey and urged the striker to "keep believing in himself".
The England international celebrated his first Barclays Premier League start for six months with the late winner.
Houllier said: "All players need confidence. Strikers need more confidence. Everyone loves Emile at the club, he is a good team-mate. What he needs is to keep believing in himself. I don't know whether he believes in me but I believe in him.
"That is more important. Because he plays up front and sometimes misses sitters, people get on his back and maybe that has hurt him in the past. But Emile fights for the ball in the air, tries to keep it and links up with the midfield. His work-rate was phenomenal."
Source: PA
Source: PA