Here in America, GMOs are legal and very common: most of the calories in the average American diet are from GMOs. In theory, I don't have a problem with GMOs: I think that they might ultimately help us feed more people more efficiently, with less environmental damage. However, I dislike several particular facets of GMOs. By far the most common modification is "roundup-ready", which makes food vegetables immune to the herbicide glyphosate. This allows farmers to spray their fields with huge amounts of herbicides instead of using other methods of weed control. I'm much more concerned by the health and environmental consequences of pesticides than I am with those of GMOs, but very often the two go hand-in-hand.
In addition, the rise of GMOs has reduced the variety of plants we cultivate, and old heirloom vegetable varieties are disappearing from lack of use. I think that this is sad and shortsighted.
Despite that, I do believe that intelligent use of the right kinds of GMOs could allow us to grow more food on less land with less water and fewer pesticides and fertilizers, all of which would be good for both humanity and the world.
I think you missed the point in what I said. Even if there are no bi-products, the purification of a substance is something that is a challenge and it's not done with 100% accuracy. This is why many industries are considered high-tech and only a few countries have the required technologies.
And no, that's not true. There have been numerous cases that have made it to the market but were harmful. Several pharmaceuticals in international markets and the US market which had had the approval of the FDA and local regulating bodies later had to be withdrawn and discarded from markets worldwide.
For example, Terfenadine was an antihistamine that was widely prescribed when it was first introduced to the market. Later, it had to be withdrawn because it could disrupt the electrical rhythms of the heart. It was replaced by Fexofenadine. Another famous example that was popularized by Walter White in the awesome TV series Breaking Bad was the tragedy of Thalidomide which you can read about it online. It's a good example of why chirality is important in chemistry and it's a good example of how things can go terribly wrong.
I understand that your story about water is supposed to be ironic and satirical, but water is an inorganic compound. It doesn't contain nucleic acids to be genetically modified.
The thing is that in most cases, there are several different chemical pathways and reactions for producing the same chemical compound and each pathway can produce different bi-products. Biological pathways are efficient because they have happened in nature for thousands of years and we know that they are compatible with our bodies because organisms where these biological reactions take place have survived. Several chemical pathways can produce the same product we desire, but we should worry about the bi-products that are produced during these processes. Some of them may be carcinogenic. Some of them may be toxic in high doses. Some of them may intervene with other chemical processes in an organism. And even at the end, we are not able to purify the substance we need with 100% precision.
At the very least, when you want to genetically modify an organism, you have to develop biological vectors to transform the modified gene into the organism. Usually viruses or bacteriophages are used. Even after having done that, there are things that can go wrong. For example, dolly the sheep that was the first cloned mammal --and we had only cloned it without modifying its genes-- had severe respiratory issues and died earlier than a normal sheep.
Dolly the sheep is a good example of why natural ways are safer. We hadn't even modified any of dolly's genes, but yet dolly suffered from severe health issues.