I think that this is true, but also that this is true not only for psychologists, but for people in general - we should be taking the most ethical decision in any circumstance. However, this might be problematic, as people disagree about what is ethical - still, considering ethics in decision-taking is a good way of maximizing people's benefit and making sure we are not hurting anyone
So the statement is true.
I would say that however, psychologists have even more responsibility to make ethical decisions because they are specifically trained to do so.
The answer is: reversing the current direction will cause the force deflecting the wire to perpendicular to the magnetic field but in the opposite direciton.
