In a utopian world, I would agree with the author. However, we do not live in utopia - we live on earth with governments of ALL countries employing as many engineers as they can afford to design better and more effecient ways to kill (and defend themselves). Some of those people are even the doctors the author is describing (building biological weapons).
For as long as humans have existed, there has been conflict. It is a basic human right to have the ability to defend yourself (as a person or community) from agressors and it is these problems that engineers are working to solve.