"Maybe because he can tell someone he gave a decision against one of the biggest clubs in the world."
Hooper thought it would be difficult for McDonald to referee a Celtic game again.
"We'd maybe not trust him," said the striker. "He might make a decision that is going to be everywhere three weeks after the game again."
Asked if he thought that McDonald should resign as a result of admission of lies, Hooper said: "It is up to him. It depends on what they decide.
"He said in the paper that he has lied to the gaffer and everyone else, so it is a big decision.
Hooper (left) promoted a fashion event with businesswoman Michelle Mone
"The ref's made a mistake. He came out and said he lied about it and you have just got to let other people deal with it."
Hooper also insisted that the penalty against United should not have been overturned by McDonald in the first place.
"We got the three points," he said. "It would have been a different story if it had been a draw.
"He has got me and then the ball. He has got me first, took me down first and pushed the ball away."
Hooper thought that Celtic had to rise above refereeing decisions.
"I think all the big teams get it and you don't see them going against it," he said. "They just get on with it and win games."
Celtic narrowed the gap on Scottish Premier League leaders and reigning champions Rangers at the weekend after a 3-0 win over St Johnstone.
"It is only one point now after they drew with Inverness," added Hooper about Celtic's title chances.
"There are loads more games left and we have a good chance. You would not have thought they would have drawn with Inverness."
Meanwhile, former referee Stuart Dougal admitted that he likes to see referees have "the bottle" to give decisions against big clubs.
"I personally like to see referees giving strong decisions against Rangers and Celtic at their home grounds," he told BBC Scotland.
"So, when I go and watch some of the younger referees performing at Celtic Park and Ibrox, I love see them having the courage to give the decision as they see it - not the way the crowd would expect a 50-50 to be given."
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