Villa were leading United 1-0 until the 51st minute when Douglas Luiz was adjudged to have fouled Paul Pogba.
Bruno Fernandes stepped up and equalised, scoring his 13th penalty across all competitions this season – the most any United player has scored in a single campaign from the spot ever.
Mason Greenwood and Edinson Cavani handed Unite victory in another comeback win for the Red Devils, while the Villans had Ollie Watkins sent off late on – the England striker shown a second yellow for diving.
That decision only added to Smith’s anger when he spoke post-game.
He told Sky Sports: “I don’t think anybody knows, everybody is confused how Raheem Sterling can go through and have four or five touches on him last night and not get a penalty, then one touch here and it is a penalty – it looked a pathetic decision to me, but he goes down, similar to Old Trafford and last season here.
“Ollie Watkins has got sent off for a second yellow, there is no way the referee can tell me he is convinced he hasn’t been touched.
“I just don’t understand the decision-making of the officials and more importantly at Stockley Park.
“It looks like now he has to get hurt to win the penalty – is it enough contact for a penalty, no.”
The win means United have moved within 10 points of league leaders Manchester City, whose title celebrations remain on ice.
While Villa are 11th after recording 14 wins out of 34 league games this season.
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