Speaking Saturday on his "Coach's Corner" segment on Hockey Night in Canada, Cherry said the suspension handed down to Thornton for attacking Pittsburgh Penguins defenceman Brooks Orpik last week was too long.
Cherry said Orpik had to "pay the price" for his earlier hit that knocked Bruins forward Louis Eriksson out of the game.
"If you hit like that, and you act like that, be prepared, somebody's coming," Cherry said. "Orpik, I feel sorry for him, he got a concussion, but if you hit like that, be ready."
Cherry went on to add that 10 games would have been enough for Thornton, who went after Orpik during a stoppage in play, slew-footed him to the ice and punched him twice in the head.
Orpik was taken off the ice on a stretcher and transported to hospital.