The MTOW on a 172R is about 2,450lb. If he would have taken off 80lb over the limit...that would put him about 3.3% over the MTOW.
That would be the equivalent of a 747-400 (875000lbs mtow) taking off 29,000lbs over mtow.
The pilot made the right call. If you were there a bit early you could have gone up for 1 hour and burned off some of that extra fuel (80lbs = roughly 14 gallons) but since that didn't happen...don't put your life at risk.
As others have said...you don't want to end up being on the front-page of your local newspaper.