This claim is empty sales talk. Genetic engineering is simply an extension of traditional crossbreeding. Genetic engineering transfers genes between species that could never be crossbred. Also, crossbreeding lets nature manage the delicate activity of combining the DNA of the parents to form the DNA of the child. Genetic engineering shoots the new gene into the host organism without reference to any holistic principle at all.
Genetic engineering is safe.
In the case of genetic engineering, there has not been the time or the public debate essential for accumulating sufficient experience to justify any broad claim to safety. The technique for inserting a DNA fragment is sloppy, unpredictable and imprecise. The effect of the insertion on the biochemistry of the host organism is unknown. The effect of the genetically engineered organism on the environment is unknown. The effect of eating genetically engineered foods is unknown.