Moyes, 50, said his side were "beginning to laugh at" referees for their "terrible" decisions.
"We're having to play them as well as the opposition at the moment," he added.
The Scot had accepted the FA's misconduct charge and requested not to attend a subsequent hearing.
Moyes upset with refereeing decisions
Referee Andre Marriner awarded a second-half penalty to Sunderland, which Fabio Borini converted, to confirm United's third defeat in a week - the first time they had suffered three straight losses since May 2002.
The former Everton manager was also angered by a decision during the Spurs defeat, saying it was "scandalous" United were not awarded a late penalty after goalkeeper Hugo Lloris challenged Ashley Young in the area.
Liverpool manager Brendan Rodgers
was recently fined £8,000
over comments he made about referee Lee Mason after his side's defeat at Manchester City.
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