Wasn't there a HN post/thread a week or so ago about some scientist having a (new-ish) theory about DNA and the role specific genes play? If there's enough doubt that there's still room for other theories, is CRISPR really a good idea?
The issue I have with this type of engineering is there is no means of egress (if you will), no thought about how a recall would be implemented.
Humans are flawed. The history of engineering displays those flaws. But instead we purposely stand in our own blindspot and insist "no. THIS time I'll be different" completely forgetting the countless times that was said previously.
Long to short, our certainty is likely overstated. It wouldn't be the first time either.