If a daycare center already takes children with disabilities and can't take more, then it can refuse to take your child. For example, if the center already has 4 children with behavior problems, it is not discriminating against the disability. The center just can't take another child.
Try to think of ways to work with a daycare center. If you can find a way for your child to be in the program without making extra work for the staff, then even a daycare center that has not had children with disabilities before might take your child.
A PCA for your child might make the difference. You could also give the staff very detailed instructions about food. Or, you could offer to pick your child up early or have them in special education programs for part of the day. If you and the daycare center work together, you may be able to get care for your child without having to get legal help.