This is not an attitude exclusive to progressives. The chief grievance here is that the historical “solution” to the “problem” of Down Syndrome has been abortion. Opposition comes from the pro-life movement (which is generally conservative) and disability advocacy groups (which are generally liberal).

A novel therapy that does not result in the termination of the pregnancy might satisfy the conservatives, but it does nothing to satisfy the disability advocates, who point out that these kinds of technologies fundamentally normalize the idea that they should never have been born the way that they are.