If man was making said changes at the rate random useful mutations tend to occur in nature I don't think anyone would be concerned. And we typically do more than just tweak a genetic component in a single individual and see how it fares against existing populations - if the change suits our short term goals, we'll do everything we can to ensure that becomes the dominant variant, often destroying the genetic diversity that provides long term durability in the process.

Any mutation could be "dangerous." We're just used to a system that produces mutations randomly so we estimate the danger to be in the background. Targeted changes also can produce unknown side effects, which to my understand are what non-GMO folks fear. Toxicity, missing nutrients, etc. could certainly be issues with adjustments, but I don't think the right approach is to fear so much as to attack things two fold: test the biological systems outputs, and learn the biological systems outputs sufficiently to simulate impacts.

If man makes the change he installs DRM into the GMO.

Because man like to make mistakes at scale.