when to introduce tech on the market and when to let human scientists discover stuff

example: when graphene desalination or equivalent technologies are introduced on the civilian commercial market, that would make agriculture much more efficient and eliminiate thirst, likely saving hundreds of millions of human lives 

but when graphene technology or equivalent technologies are introduced on the civilian commercial market that would also produce vastly more lethal weapon systems which would kill hundreds of thousands of humans in different conflicts or wars 

of course humans will likely die in conflicts or wars anyway with the use of rifles and similar 1800's weapons technologies