Aston Villa captain McGinn, whose brother Paul plays for Motherwell, was critical of the decision to dismiss Gordon.
“I’ve sent you to the screen let’s send you to an angle from the North Sea to back it up,” he wrote on social media. “Scottish var is a mess.”
Pundits also had their doubts over the third red card, with former Fir Park captain Stephen Craigan telling Premier Sports there was a “grey area” surrounding a foul so far from goal, while ex-Aberdeen skipper Willie Miller described the challenge as “cynical” before adding: “Was it denying a goal-scoring opportunity? I’m not so sure.”
Motherwell manager Jens Berthel Askou had no issue with Priestman’s dismissal but was stunned by Gordon’s exit at the beginning of the second half.
The Dane told BBC Scotland: “We get Liam Gordon sent off in a decision that is a mystery to me and will remain a mystery to me because there are two players covering behind him who will, without a shadow of a doubt, get in his way or at least make sure it’s never a very obvious goal chance.”
The Scottish FA has been approached for comment.
The Priestman and Gordon dismissals follow similar incidents in Dundee United’s cup win over Spartans on Tuesday and Falkirk’s Premiership defeat by United on Saturday.
Falkirk’s Liam Henderson was initially shown a yellow-card for a foul on Max Watters near halfway but that changed to red following a VAR review.
At Tannadice, United centre-back Iurie Iovu was sent off for a bodycheck on Cammy Russell, with the referee issuing a straight red.
