There are a lot of risk reduction reasons and also a lot of ethical and moral reasons. These are all legitimate and worth considering, and hopefully another commenter or two can elaborate and point you to resources.
But I want to take a moment to highlight the legitimacy of sentimental reasons in this case.
Humanity is an important and closely guarded trait, for reasons that some have characterized as "self-evident". One could characterize "civilization" largely as a mechanism for preserving humanness and helping it flourish. When it comes to deciding the genetic fate of the species, these rather sentimental ideals about what makes life worth living are perhaps one of the most important decision criterion.
Humanity is also suffering, pain, despair, hate, agony, torture.
Human condition is indivisible from suffering. Such is life they say. For millenias humanity has not made a significant number of its individual members happy or fulffilled.
Humanity as something immutable is in its waning years. And I won't mourn for it. The posthumans are coming. Let them come faster.
Frankly, it is precisely because of the human condition that technologies like this are dangerous. What happens when a misogynist wants their daughter to have a reduced sex drive, or a fundamentalist government wants its people to be more religious. If we have this capability, it will not go well.
It doesn't go well now, at this very point in time.
>misogynist wants their daughter to have a reduced sex drive
Number of instances of female genital mutilation is absolutely insane.
>fundamentalist government wants its people to be more religious
ISIS. Saudi Arabia. Russia. Propaganda and state religion works well enough. There is no need to look far from HN to see how governments prop up religious beliefs in general populace. "In God We Trust" on US dollars and "under God" in pledge of allegiance are a few fine examples.
And frankly, human genetech and biotech modification can't be stopped, neither by laws or popular opinion. The incentives are just too great.
It's natural that an intelligent agent would defend against modification to its current primary drives, but the thing about changing your mind about what you want is that once you've done it you no longer care about your previous drive. I find it hard to think of reasons why we'd rationally object to changing our fundamental motivations, since we wouldn't care after we did it. There's no real reason to object other than a craven appeal to self-preservation taken axiomatically.
But I want to take a moment to highlight the legitimacy of sentimental reasons in this case.
Humanity is an important and closely guarded trait, for reasons that some have characterized as "self-evident". One could characterize "civilization" largely as a mechanism for preserving humanness and helping it flourish. When it comes to deciding the genetic fate of the species, these rather sentimental ideals about what makes life worth living are perhaps one of the most important decision criterion.