Could they have been unloaded at the hardstand? Sure. But what means were there for getting those folks over to the terminal? Walking a couple hundred yards across taxiways isn't exactly smart.
They should have unloaded the plane at the hardstand and walked them up to the terminal. We're talking about spending nine hours on an MD-80 not a DC-10 or 767; a plane that is designed for such durations. There couldn't be any food service, they probably only had the stuff for maybe two beverage services, and we all know how nasty the lavs get on transatlantic service on the widebodies; just imagine how bad it would be on a plane that's designed for nothing longer than a four hour run! As for the safety, its not like they are walking across the ramp at O'Hare or LAX. This is Austin we are talking about. It's a pretty quiet airport. Someone at American should have lost their job because of this.