WIRED Bodyhack has a fun blog on Genetically Engineering Your Child's Sexual Orientation. The basic issue is a southern baptist blog by Albert Mohler suggesting that if it was possible to alter a baby's sexual orientation prenatally it would be proper to make it heterosexual. As pointed out by Bodyhack, this is a tricky issue for pro-choice people: would they accept abortions of fetuses based on their orientation?
Pro-choice and anti-selection attitudes seem to regularly collide, and genetic councelors have a hard time resolving these contradictions. On the other hand, being pro-life and for selection would require being for germline modification or other rather invasive processes in utero, something which goes against the conservative ethos the pro-lifers generally adhere to. Maybe the solution is to adopt away the gay babies.
As a libertarian I'm of course pro-choice and pro-selection.
However, there is an even funnier twist here. Would Albert Mohler support interventions to promote religious babies?
Twin studies show that religiousness has a reasonably strong heritability, about 44%, and that it increases with age (i.e. people develop to their genetic level of religiousness). See also this, this, this and this paper. There is also a negative correlation between serotonin binding and 'self-transcendence', a personality trait covering religious behavior and attitudes. Presumably, by setting the density of serotonin receptors and other correlates of spirituality the adult religiosity of children could be influenced. The heritability looks a bit lower than for sexual preference, so it would still be rather random - or with space for free will, if one wants to interpret it charitably.
Given that Mohler claims that "we should unapologetically support the use of any appropriate means to avoid sexual temptation and the inevitable effects of sin", it seems equally reasonable to support the use of any appropriate means to develop faith and spirituality. And since faith in his system of thought (I think) ought to be a way to reduce sins (or their effects) any means OK to apply for reducing sins ought to be OK to apply to increasing faith.
Of course, the flaw in this is that the particular religion of the child is not set. While the choice of religion tends to be heavily affected by upbringing there is no guarantee that the child will remain within the fold. Self-transcendent people may be fulfilled and humble enough that they do not stray often, but some will no doubt convert to religions their parents find distasteful.
Would the selection rob the child of free will? I don't think so. What is being set is parts of personality traits, not the thoughts or reactions of the emerging person. They will bias and affect the thoughts, but no more and no less than any other personality traits. That these ones were selected does not give the parents more control over the child or predetermine its destiny.
A theological argument against would be that God would make sure to give the right genome, and that parents should trust God to do it right. But if that is true, then God seems to like gays too.