The Responsibility of a Scientist

A scientist should assume responsibility for the fruits of his work. I would not argue against this, but it must clear to all of us how very modest such assumption of responsibility can be, how very ineffective it has been in the past, how necessarily ineffective it will surely be in the future. 

-Opennheimer 

Could scientists be held responsible for the way results are used?

Opennheimer answers this question himself, "Despite the vision and the far-seeing wisdom of our war-time heads of state, the physicists felt a peculiarly intimate responsibility for suggesting, for supporting, and in the end, in large measure, for achieving the realization of atomic weapons. Nor can we forget that these weapons, as they were in fact used, dramatized so mercilessly the inhumanity and evil of modern war. In some sort of crude sense which no vulgarity, no humor, no overstatement can quite extinguish, the physicists have known sin; and this is a knowledge which they cannot lose." 

• In short, scientists must held responsible for the way results are used. I also agree with Opennheimer, choices means responsibility, and responsibility bears the morality of the action.

Should certain areas of physics be avoided because of possible destructive use? 

For me, it is a yes because as long as these bombs exists and are still studied, we are under a great threat.  A tremendous impact can happen! To further justify my statement, let us watch this video: 

From their own observations and from testimony of Japanese, members of the survey team divided the morbidity and mortality of the atomic bombs that were dropped on Japan into the following phases:

• Very large numbers of person were crushed in their homes and in the buildings in which they were working. Their skeletons could be seen in the debris and ashes for almost 1,500 meters from the center of the blast, particularly in the downwind directions.
• Large numbers of the population walked for considerable distances after the detonation before they collapsed and died.
• Large numbers developed vomiting and bloody and watery diarrhea (vomitus and bloody fecees were found on the floor in many of the aid stations), associated with extreme weakness. They died in the first and second weeks after the bombs were dropped.
• During this same period deaths from internal injuries and from burns were common. Either the ehat from the fires or infrared radiation from the detonations caused many burns, particularly on bare skin or under dark clothing.
• After a lull without peak mortality from any special causes, deaths began to occur from purpura, which was often associated with epilation, anemia, and a yellowish coloration of the skin. The so-called bone marrow syndrome, manifested by a low white blood cell count and almost complete absence of the platelets necessary to prevent bleeding,w as probably at its maximum beTween the fourth and sixth weeks after the bombs were dropped.

Here is an interview Theodore Van Kirk, the last living member of the Enola Gay crew who dropped bombs in Hiroshima:

65th Anniversary of the Bombing of Hiroshima: