Gallen said ex-Canberra flyer Joel Monaghan was still reminded of his off-field behaviour six years after he left for the UK Super League when a photo emerged of him simulating a sex act with a dog during Raiders' Mad Monday celebrations.
"The unfortunate thing for Mitchell is that he has to live with this forever," Gallen told Sky Sports Radio.
"This is something that is not going to go away for him.
"It will live with him for the rest of his career which is hard enough.
"It's like the Monaghan thing. They still carry on about that overseas."
Gallen admitted he did not know what an appropriate sanction was for Pearce but hoped the star No.7 did not suffer the same fate as Monaghan and another former Rooster Todd Carney.
Carney also linked with the Super League after his NRL banishment for his infamous 2014 "bubbler" incident.
"I think it is important that they take their time with this one," Gallen said.
"I think they have rushed into a few in the past - the Todd Carney one ... (for example).
"But do I know what an appropriate sanction is? I really don't.
"I am sure the sanction will be harsh - we will wait and see."
A final decision on Pearce is unlikely to be made in the near future, given both the governing body and the Roosters are without a CEO.
The fact that fellow NRL club Cronulla are also in a Supreme Court battle over Carney's axing will also ensure due process is fully followed.
Pearce has since checked into an overseas rehabilitation clinic to address his alcohol problems.
- AAP
