So, you think that we can’t figure out the rest? Or do you think that, if this manipulation becomes accepted and commonplace, we can still prohibit other manipulations, simply because they aren’t the same type of manipulation?
Do you give no weight to the “slippery slope” argument, or do you simply not mind if we go down that slope?
We do manipulations all the time. Choose an attractive healthy partner over an ugly or sickly one, and you’ve just done genetic manipulation. Choose a partner who’s tall like you, instead of short like you aren’t, and you’ve just done genetic manipulation. And in some Orthodox Jewish communities, where the rabbis are doing genetic testing for Tay-Sachs and then not approving any “matches” between men and women who are both carriers, they’re doing genetic manipulation (and interestingly, they do it without telling the individuals the results of their own tests).
I don’t think we should be prohibiting any kind of genetic manipulation which is done under the direction of free citizens at their won expense, because it’s inconsistent with freedom. While I personally think it’s irresponsible for people for who are carriers of severe genetic diseases to reproduce without availing themselves of reliable techniques to avoid passing on the disease, I don’t want the government involved in the decision (nor do I want the government or taxpayers socked with the bill for the results). I don’t think government has any business requiring people to use such techniques, nor prohibiting them from using such techniques. Stupid stuff like choosing eye color or trying to breed a football star will never catch on widely and will be a passing fad among fools who are easily parted from their money (and will result in amusing new brands of youthful rebellion). Serious stuff like preventing the births of babies with severely disabling genetic defects, or deliberately choosing to have babies that carry less severe defects that their parents have (as one deaf lesbian couple in the UK did) is too important a matter to have government meddling in.
Most people, left to make their own free choices will steer clear of the extremes. And as for the few who won’t, the results can’t be any worse than the results of nature’s own errors, which include babies born with no brains, babies born with most of their organs outside their bodies and improperly developed, babies born with with horrible disorders that result in short lives filled with nothing but pain an suffering, babies born with two bodies fused together but only one heart which can’t support the whole fused system, etc.