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.
Referee Jon Moss was not fooled and promptly cautioned Young, although he later awarded a penalty when the same pair tangled again, even though some observers felt the latter incident warranted another caution.
The first was far more clear cut though and left Moyes feeling less than comfortable.
"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.