^^^Being fundamentalists, probably something like "it's the work of Satan".
From the linked article:
"You're getting into unsettling ground that I think is damaging to our sense of humanity," says Stuart Newman, a professor of cell biology and anatomy at the New York Medical College.
I would say challenging, rather than damaging. As in, what exactly does it mean to be human, biologically, legally and so forth? For instance, it turns out it's possible for some people to have more than one distinct genome, "natural" chimeras:http://www.babycenter.com/0_strange-but-true-one-person-born-with-two-sets-of-dna-a-chim_10364937.bc
Obviously these individuals are regarded as human, despite being markedly different than most of us at the genetic level. As that article concludes, that may be more common than was previously assumed. So if we currently recognize such variations as part of the human spectrum, is it that great a leap that someone with genes deliberately
inserted into their genome could also be recognized as human?