hmmmm arguements against
past mistakes have lead to a increased risk to humans. a genetically engineered brazil nut was withdrawn from sale 1 day before its launch as a toxin was found within the nut, which was harmful to humans....
a food substitue made from crude oil was fed to animals, but this led to an increased cancer incidence in the animals and whoever consumed them
genetic engineering plants and animals narrows the gene pool making a cataclysmic event more likely
we are toying with the code to life that can be argued is divine and can only be fully understood by he who is divine (god)
if someone brings up gene therapy bring up a kid who had an adenovirus attentuated so DNA could be inserted into his cells (forget where or why)....the virus wasnt weakened enough and it killed him (dwell on the horrific effects of the virus such as te oragn swelling and explosion and massive oedema of the body plus high temperature and burning sensation, its what right winger do when they attempt to justify something even though it only happened once or twice

)....this only happened once btw
the abiltiy for humans to kill each other is only enhanced by this knowledge
people may seek to pervert this knowledge for evil ways (i.e. using genetics to discriminate etc)
legally patents may be placed on things every human has (the genome, specific chromosomes etc).....american companies LOVE doing this
we could create something that coud kill us (i.e. parastites killed by other animals have a knock on effect on the food chain)
private companies are usually able to undertake such research and spend more money than public/charity teams and as such choose what gets studied, and what gets cured. capatalism may have president over health benefits (i.e. a cure to aids)