The whole point is that wearing masks DOES harm some people specifically due to disability. And, again, facilities and services that are open to the public should not create barriers based on disabilities. Further, its easy to say, "you don't have a right" to equal access to Disneyworld, but what about the grocery store? The court house? The hospital? (The hospitals in our area and the Department of Health recognize some people aren't able to wear masks, and make accomodation.)
I would also point out that limiting accomodation this way basically says that people with disabilities must surrender their right of access in order to protect others. I would point out that historically in the battle of rights the disabled were often the losers. Remember a random law about growing wheat in someone's yard was the turning point for courts to uphold the individual mandate. Those pain in that patootie autism kids with their show boat parents just might be the canaries in the coal mine.
My final point for those who see no harm, try walking in the other shoes. Try making a mask out of a brillo pad-nice and tight- be sure the ear loops pull on your ears, turn Demon Hunter on full blast, while a clock ticks next to you ear, have someone shine a bright flashing light in your eyes. Now you could just set a time for the experiment, but then imagine you have no real concept of time and for you each second is an eternity and torment will have no end.
ETA: There are accommodations under the law for people who can't wear a seat belt in a car. At amusement parks, if someone can't ride a specific ride, they can still access the park. Here we are talking about complete denial of service based on disability. Based on there now/just back threads, and Disney rules, not everyone wears a mask at all times. Some have chin mask, but aren't booted from the park, some are younger or appear to be younger than the requirement, yet are still allowed in the park (based on the same CDC exception that applies to for those with a disability), people can stop and eat and drink....I suspect no one has told the virus not to spread during those moments. Plus other parks and facilities have been able to offer individual accommodation.