Ford and Gray were handed the bans after being cited over a dangerous tackle when the duo cleared out Jack Lam at a ruck during Scotland's pool victory against Samoa last Saturday to secure their quarter-final against Australia.
A team spokesman expressed "disappointment" at the ban, which was reduced from an initial five weeks to three because of mitigating circumstances, and Scotland were considering an appeal pending a review of the full judgement.
Former winger Logan, however, contrasted the ban with an off-field yellow card handed to Australia's David Pocock for a knee in the back of Wales hooker Scott Baldwin and a one-match ban handed to Ireland flanker Sean O'Brien for punching a French opponent.
"This is a sick joke. Pocock clearly knees Baldwin in the back but gets off with a slap on the wrist, and Ireland’s Sean O’Brien gets a week ban after a premeditated punch on Pascal Pape in full sight of the referee," Logan told Britain's Daily Telegraph newspaper.
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'SHAMEFUL DECISION'
"Two Scottish players with a perfect disciplinary record get a three-week ban for clearing out a player with no malicious intent at a ruck just because he fell awkwardly. There is no level playing field. This is a shameful decision."
In its efforts to reduce the risk of serious head and neck injuries, World Rugby insists on heavy punishments for tackles where a player is lifted above the horizontal but not helped safely back to ground.
Scotland, who have 48 hours to appeal Tuesday's decision, face Australia in the last of the four quarter-finals at Twickenham on Sunday.
"World Rugby has totally devalued a World Cup quarter-final," added Logan, who played 70 times for his country around the turn of the century.
Australia coach Michael Cheika said he had not seen the incident but expressed sympathy for the Scottish duo in missing such a big match.
He did not think it would make the task any easier for the Wallabies, however.
"They are very influential, but I think these types of tournaments are made for people stepping up," Cheika told reporters on Wednesday.
"The guys who will replace those two are ready to roll. We understand there will be 23 players in the Scotland jersey trying to smash us. It doesn't matter the names on the jerseys."
(Reporting by Nick Mulvenney; Editing by David Goodman)
