They may not be able to control it, but you can by taking them out if they can't be quiet. Should someone with developmental disabilities get to enjoy the show at the expense of everyone around them? So, it's better that they just stay at home and have no experiences? As it is their lives are not as "full" as ours are. Imagine knowing that you'll never be able to live on your own, always having to rely on your family to take care of you, and knowing that you probably won't live as long as other people your age. To know that your parents can't even put you in their will other than to leave you to someone else like apiece of property. On top of that "regular" people don't want you in public because you might be disruptive.
What good is keeping them locked away? Thousands of handicapped adults are neglected and abused in our country. So if someone cares enough about their friend or family memberout to give them the fabulous experience of live theatre good for them. Handicapped Americans should not be kept away because they might bother you.
Sorry if the noise bothers you but they're a part of our community just as much as anyone else. They have every right to be there. Instead of being annoyed by their behavior you ought to be grateful that you have all of your facilities and have the life that you have.
And comparing people who willfully take out their cellphones or whatever to the handicapped is incredibly short-sighted.
"All our dreams can come true -- if we have the courage to pursue them." -- Walt Disney
We must have different Gods. My God said "do to others what you would have them do to you". Your God seems to have said "My Way or the Highway".