He described this as a 'solution to a ticklish ethical problem'.

Some people have an ethical problem eating horse and will feel betrayed to learn they've eaten it.

Billy has an ethical problem with the request, and refuses it.

Assigning a subject to a placebo group can pose an ethical problem if it violates his or her right to receive the best available treatment.

Mundane situations pose novel engineering and ethical problems, but they also lead people to question basic assumptions of the traffic system.