To quote from Jurassic Park.
Genetic modifications can be very dangerous to use and the process should not be taken lightly. Genetic diversity could be disrupted by GMO's and once a mutation is introduced it would be exponentially harder and harder to destroy as generations went on. It's been proven in a few tests that eating GMO's can cause serious further generational problems in rats, so us humans should watch ourselves carefully.
I'm not saying we should never modify things whether those things be plants or people. But we should go about this very very cautiously. While genetic modification is not itself bad specific modifications could potentially trigger things that are dangerous we might not notice right away. That goes for crops, livestock, and ultimately humans.
With humans we have to be especially careful. It's especially troubling that people tend to think in oversimplified black/white terms about genetics and articles are slanted towards that way of looking at it.
They can find a genetic correlation and many people talk about it as though the thing were 100% genetic.
Yet sometimes they are not 100%. And a gene can influence things indirectly. A gene could code for X which when exposed to certain conditions (perhaps many conditions) later in life leads to Y. In that case we should know more about the process before modifying anything. It may be that it's better to change the factors that lead to a negative outcome rather than changing the gene itself. Changing the gene itself may be "throwing the baby out with the bathwater".
And genes can also interact with each other. Genetics is far more complex than people usually think about it. Genetics is promising but needs to be handled with caution.