Lambert dismissed that assertion at the time, emphasising he had "never sent anyone out to kick" a player on the other side.
And he had stronger words on the matter when asked about it on Thursday at his pre-match press conference for Saturday's league trip to Stoke.
"You look at our lads in the team and they are not big, aggressive lads," Lambert said.
"There are one or two who can look after themselves, but if you are talking about the midfield zone, there are not many there.
"You can't just let anyone turn up and try to play, but we are not a team of kickers at all. I think that was unfair."
The loss to United was Villa's second in a row, with them being beaten 2-0 at Fulham a week earlier.
Lambert is in no doubt, as he prepares for the hectic schedule of games that begins with the Stoke contest and will take Villa through Christmas and into the New Year, that the way his team performed in those two matches was not good enough.
But he is certainly not getting too down about how Villa are faring overall this season, his second campaign in charge.
The midlands outfit are currently 11th with 19 points from 16 games, whereas around this time last term - before they went through what proved to be a nightmare festive period - they were lower down the table.
And Lambert said: "We have had two performances, against Fulham and Manchester United, where we weren't good enough, and that is the bottom line.
"But against Southampton (Villa's previous game, which they won 3-2), I thought we were excellent considering the way they have been going.
"The start we have made to the season has been pretty okay.
"You can't let two games be a real bugbear.
"You have to let them go, and we'll go up to Stoke and try to win.
"The good thing about the group is that while they can feel down after games, you get them back at the training ground and you can get them up again.
"You are hoping the fans look at it as you do yourself - you have to let games go, whether you win, lose or draw. You can't dwell on them."
Forward Gabriel Agbonlahor will definitely not feature against Stoke due to suspension after picking up his fifth yellow card of the season in the United game, but Fabian Delph is set to return having now completed the ban he was serving for the same reason.
Fellow midfielder Chris Herd should be back available after a facial injury meant he missed out on Sunday, but Lambert says captain and defender Ron Vlaar, who has been nursing a calf problem, is "still a major doubt".
Meanwhile, another centre-back, Jores Okore, may well be ready to return to action before the end of the campaign.
Villa announced in mid-September that Okore could be sidelined for up to nine months after the 21-year-old Denmark international sustained a ruptured anterior cruciate ligament injury in his right knee in a match against Newcastle.
But a message on Okore's Twitter account earlier this week said: "I may be back this season!!!"
And Lambert said on Thursday: "He's doing great, really well with his rehab.
"Hopefully with a bit of luck he'll play some part of this season."