Somehow, I doubt that the situation is as dramatically shameful as the "petition" makes it to be. I'm sure it's very difficult to build a facility with totally flexible seating accommodations. It seems admirable that the venue has spaces for wheelchair users and the people who attend them. To accommodate an uncertain number of people accompanying a wheelchair, may be too much to arrange for in a single event.
So....flexibility and goodwill is needed by all. Such matters are not handled well by confrontation.

-Joe-