I don't see this as a disability bashing thread because it's not a clearcut disabled access issue. It's looking at how a range of access needs are catered for in a setting like a theatre. this is MN. It wil absolutely turn into an increasingly disablist thread and you know it.
In terms of reasonable adjustment, people are misunderstanding the term. A reasonable adjustment isn’t expecting everyone else to change their expectations to accommodate the person with a disability, a reasonable adjustment is an adjustment made in order to accommodate the perso with a disability.
So e.g. the reasonable adjustment would bbe to have a performance which is suited to the needs of the people who need to make noise. And for the terms to stipulate that noise won’t be permitted throughout the regular performance, but this needs to be stipulated to everyone at the time of booking, so that when you book you know what you’re up against, and you know that the expectation is for no noise.
So the group with the shakers are welcome to attend the regular performance, but if they want to use the shakers they need to attend the specialist performance, assuming there is one.
Let’s use another example. Guide dogs are permitted in most places, however they are not permitted in many zoos or parts of many zoos because of the stress caused to the animals. The reasonable adjustment tere is to say that the guide dog owner is welcome to bring the dog, and the dog will be looked after by the staff, while the guide dog owner can either go around with their own guide or the zoo will often provide one. Perfectly reasonable adjustment.
Also, the people saying that the group were incredibly selfish need to think about what they’re saying. A group of people who are shouting, using shakers, making noise throughout a performance very likely don’t have the same capacity as you or I, so if there is any responsibility to be had, that responsibility falls to the people who are caring for that group, not the group themselves.