I have a child with a disability, he has said inappropriate things without being aware, because he saw them in movies or on television and people thought they were provocative or funny. but I would be devastated if I found out his school was throwing him into a locked room, terrified about what he didn't know what he had done. (They are not, our school district is actually terrific, and fellow students have treated him wonderfully.)
I certainly get that while my child is not violent, some are, and schools are often used as daycare - some members of Congress even want school hours expanded to be actual daycare - so parents abdicate a lot of behavioral modification to government, but Illinois allows it for "for safety reasons only" and that was clearly not the case. It's better than the old days, when they'd put disabled kids in a 3' square box, but guidelines are of no use when schools routinely violate them.
Teacher unions see the writing on the wall, even as they have to recognize it is often teachers forcing this kind of punishment. Good for them. This is not politics, this is child abuse.