These days, everyone knows about terrorism. Unfortunately, genetic engineering could easily be used to make organisms that kill people by infecting them with new types of disease. Or they could be used to infect and kill food crops or farm animals. Then people would die of hunger. I find all this really scary as I expect you do. Pretending there isn't a problem is not the answer.
Many countries have already experimented with what is called biowarfare - using living, disease-causing microbes to cause plagues to kill people. Countries have recently come together to try and agree on an international treaty which would ban such horrors. Unfortunately, not all countries agree with the treaty for various reasons. One reason is that to be useful, such a treaty would have to allow teams of inspectors to visit any laboratory in any country to make sure that no biowarfare organisms were being made. After all, without proper checks an agreement would be useless. And some objecting countries think that such inspections would be like spying and could give unfair advantages to others. As ever with humans, there are no easy answers. But something has to be done for sure - as the 2001 anthrax attacks in the US show. There are many much more dangerous organisms than anthrax - and that's without genetic engineering.
Australian scientists recently accidentally created a monster while they were trying to engineer a mouse virus . The idea was not to harm the mice, but prevent them having babies. Not only did it not work. It killed the mice. Not too worrying, you might think; they were only mice. But it would be easy for a laboratory somewhere to secretly engineer a similar virus which infects humans and kills them. This would one way of using GE for making a deadly biowarfare agent. There are many others. Really scary.
1. 'The genie is out: Biotech has just sprung a nasty surprise. Next time, it could be catastrophic', New Scientist, 13/1/01, 3-4.