Young went down following a tackle by Kagisho Dikgacoi during the first-half of the 2-0 win but TV replays showed the United wide-man had initiated the contact. Robin van Persie converted the awarded penalty.
"I don't want my players diving," said Moyes.
"I don't want anybody doing it.
"The boy (Dikgacoi) definitely throws his leg out but I think Ashley has put his leg into his leg. It is not what I want."
Young has previously been in trouble for diving, although it was difficult to argue either way for the second offence, which triggered a penalty that allowed Robin van Persie to open the scoring and led to Dikgacoi's dismissal.
"I don't like the rule where every time it is the last man it means it is (a red card)," said Moyes.
"I thought it was harsh.
"If I was Ian Holloway I would be disappointed.
"OK, it might be a penalty. But I don't think the boy made a challenge to wipe him out.
"Unfortunately that is the rule."
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