This starts as a slight naturalistic fallacy: assuming that because something is natural, it is right. For gene editing, this is not quite the case since we have clearly defined parameters by governments, intergovernmental institutions, and others that define what a disability is. And again, with gene editing, there ought to come tightened laws around it. The argument was framed around whether or not the act of gene editing should be allowed, so to talk about "who decides this", while can be a good argument if framed well, doesn't really work here.
Lovely argument though!