I don't see why people keep spouting this as if it gives Disney freedom to do whatever it wants without guest recourse.
First, because of past precedent: Disney announces, in advance, what attractions are and are not going to be operating on what dates. People rely on these announcements to plan their vacations, plain and simple. It is reasonable for people to rely on these announcements.
Second, just because something is buried in fine print somewhere does not make it the law of the land. If Disney included the term, "by purchasing this ticket, you agree to deed your house to the Walt Disney Company" on the reverse of the ticket, certainly that wouldn't be enforceable just by virtue of it being written.
More-so than anything, I am surprised that you all don't empathize with the OP a bit more. If you were in his shoes, and you did your due diligence researching when to take your trip, based on Disney's own schedule, and Disney did not conform to that schedule without any announcement, wouldn't you be a little ticked off? This isn't a matter of Space Mountain having technical difficulties unexpectedly for a few hours or rain causing a show to be canceled--this is Disney failing to provide entertainment on certain dates that it previously indicated it would provide.