A mercy rule would probsbly be a good idea. So would holding the athletic department responsible for playing in the proper division.
Because the one thing you generally CAN'T do in organized sports is tell your kids not to give it their best. It teaches the wrong lessons about competion and is a good way to get someone injured.
Besides, apparently the winning coach had pulled his starters and was letting the bench warmers play and wasn't using any pass plays, just running plays. Not much else he could do.
Something like this happened when SMU was playing the Aggies shortly after SMU's "Death Penalty" had been completed. The Aggies annihilated them. When SMU's coach was asked what he thought about the Aggies running up the score, he blew up at the reporter- "They didn't run up the expletive deleted score! They only used 4 different plays out of their expletive deleted playbook- we just couldn't stop them!"