After all, we already use countless ways of discriminating rationally on the basis of the likelihood of future ability. If anything, genetic testing for future capacities is less objectionable because it's more reliable. Most of our current worries stem, of course, from insurance. The result could be the end of insurance pools as we know them. But it's worth noting one thing.
All insurance is about predicting the future based on imperfect knowledge of the present.
The point of genetic testing is to give us a better idea of the present and future. Young single males, for example, have a harder time getting car insurance than married middle-age women. We accept this principle as a recognition of reality. At least that doesn't extrapolate from a general population to an individual. What's happening is that the veil of ignorance that once covered our inner lives is wearing increasingly thin.