I'm aware of that. Many folks seem unaware that "discrimination" is an unavoidable and NECESSARY part of life. I chose to illustrate that fact with some extreme examples. The principle extends to much less extreme fields of endeavor ... even dance classes for small children. It is not for you, or me, or even this girl's parents, to decide the criteria (if any) for admission into this dance class for small children. It is for the proprietors of the school to decide.
At least, it is for them to decide in a free society.
I value liberty.
You?
Show me anywhere in any article that it says that the child with Down Syndrome needs anything extra or different from others in the class.
Many with Down need nothing different unless it is an academic subject.
There is no reason to discriminate against someone based solely pm their looks.