He will now face a face a fine or a warning after a disciplinary hearing.
Moyes said United were "playing referees as well as the opposition" after a 2-1 League Cup semi-final first leg reverse at the Stadium of Light, his side's third defeat in a row in all competitions.
The Scot questioned the awarding of a free-kick that led to Sunderland's opening goal and a penalty, having already said it was "scandalous" United were not awarded a late penalty against Tottenham Hotspur at Old Trafford.
"I feel we are having to play the opposition and the referees. We are all just laughing at them at the minute," Moyes said,
The matter came a week after Liverpool manager Brendan Rodgers was fined pound sterling8,000 ($13,177) and warned as to his conduct after admitting a similar charge for questioning the appointment of referee Lee Mason to his side's Boxing Day game at Manchester City.