There is a root problem with all these worries, that also comes up in most future problems projections (gray goo, human mind uploading etc).

If we come to a point where we can change someone DNA with a injection, and this ejection can continue on in the germ line. We have the technology to change it back again, because it's the same technology we used to cause the problem.

Everyone fear mongers in the idea that the scenario happens now to someone, and everyone else is stuck with our current technology.