Steven Gerrard put both spot-kicks away before almost adding a third when he hit the post after Vidic was questionably shown a red card for a challenge on Daniel Sturridge prior to Luis Suarez's late third goal.
After the match, Moyes was careful with his words when discussing the penalties but was certainly not using them as an excuse for the heavy defeat.
"I thought the real turning moment was the second penalty just after half-time," he told Sky Sports.
"To lose that made it difficult for us. There wasn't a great deal in it at half-time.
"There was a handball from Glen Johsnon in a similar position (to where Rafael was penalised for the opening spot-kick) which wasn't given. Nevertheless I can't have any qualms about it.
"There were quite a few decisions but I won't speak about it, it seems the best way to go about it. Us managers are better not commenting on decisions in games."
The loss saw United remain seventh on the Premier League table, 12 points off the top four, with nine fixtures remaining.
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