The 28-year-old McRae was playing for the Sydney-based Randwick club when he delivered the outburst to touch judge George Ayoub after a sin-binning for a professional foul, with referee Stuart Dickinson then dishing out a red card to the former Saracens player.
McRae, at a disciplinary hearing, pleaded guilty to "an act contrary to good sportsmanship", and picked up the month-long ban, which will mean him missing the rest of the Australian season.
His Randwick team are currently in contention for silverware in NSW's Tooheys New Cup competition, and face a semi-final against regular season champions Eastwood at TG Millner Field this weekend after winning Saturday's game against Sydney University 33-20, despite McRae's dismissal.
However, McRae's suspension will unlikely have a major effect on his new English club Gloucester, as the player was not going to arrive at their Kingsholm base until after the Tooheys New Cup.
Indeed, according to Gloucester boss Nigel Melville, the suspension might now aid the move.
"Duncan is now free to arrive in the UK earlier than we had planned and it will offer him time to settle in to the area and form a good working relationship with the players," said Melville.
"We weren’t expecting Duncan much before the Quins game [on October 18], but we can now planwith set dates in mind."
The Cherry and Whites acquired McRae in the off-season following the departure of Frenchman Ludovic Mercier to Grenoble, and fielded Brad Davies in the No.10 shirt in their season opening win over newly-promoted Rotherham in Saturday's Zurich Premiership encounter.