Your reasoning is that you claim to know a certain genetic "destiny" of an entire species of living organisms, and use it to call for a complete and total genocide against the species itself. Hereby totally ignoring the differences between different specimens of sais species. I don't see how this is in any way, shape or form morally justifiable.
For starters, I don't bother justifying things 'morally' in a conventional sense, since morals are subjective and not universal. What I consider to be moral is a lot different from what you consider to be moral. If I'm acting, it's because I consider it moral to act.
Looking for said individuals is more or less counterproductive. The genophage itself is a chance the Krogan blew. They had the ability to maintain a viable population with it active in their genealogy, and they let their darker nature get the better of them. Practically, they aren't worth keeping around due to their genetic propensity for insanity, psychopathy, psychosis, and carnage. To be frank, I *do* know what traits are desirable in Krogan. Their history has dictated that the most violent survive. While understandable, it comes into conflict with a more civilized galaxy. They're barbarians. They won't change. Wiping them out saves us a lot of trouble. I'm not going to take a chance that they might play fair based on goodwill. As Shepard said to the Dalatrass "You can't condemn an entire species to extinction based on what might happen". To that, I say that you can't award existence to an entire species (that have routinely proven otherwise) to a species based on what might happen.