Should bioengineering graduates seek employment in the defense industry?

They say that the difference between a mechanical engineer and a civil engineer is that the mechanical engineer develops weapons whereas a civil engineer designs targets. The implication is that some engineers are involved with building peaceful infrastructure whereas others contribute to destruction. This brings to mind the question: what is the proper role for engineers in the creation of weapons and defenses against them? In particular, should engineers specializing in biology or medicine be involved in the defense industry? After all, bioengineers are supposed to be builders or healers rather than warriors or destroyers.