the only thing I will say in their defense is that for some of these kids routines are very rigid and so once you establish a pattern, its very hard to break it. So taking away what was routine could be an issue.
I think its important to note that the GAC was not being abused by those with disabilities for the most part, but was mostly being abused by those who had no real need for one and were using it in the fashion of an infinite fast pass on every ride in the park. This was most evident at DLR where the Annual Passholder contigent makes up a large part of weekend traffic, and they were using them by the boatloads which was causing massive issues. WDW had its fair share of issues as well, including the rich families hiring disabled tour guides.
But the program ran for years with little to no issues. Its only when the internet made it easy to spread the secret of free fastpasses to anyone that it became such an issue that Disney had to do something. And in the end the only people it really hurt were those the GAC helped the most. Now does the DAS meet the letter of the law, that is up to the courts to decide.