I think a better way to frame this issue would be the following method.

1. Present your philosophical thought-experiment.
2. Ask your subject for their response and their justification.
3. Ask your subject, what would need to change for them to change their belief?

For example, if I respond to your question of the solitary traveler with "You shouldn't do it because of biological concerns." Accept the answer and then ask, what would need to change in this situation for you to accept the killing of the traveler as moral?

I remember this method giving me deeper insight into the Happiness Box experiment.

Here is how the process works:

1. There is a happiness box. Once you enter it, you will be completely happy through living in a virtual world. You will never leave the box. Would you enter it?
2. Initial response. Yes, I would enter the box. Since my world is only made up of my perceptions of reality, there is no difference between the happiness box and the real world. Since I will be happier in the happiness box, I would enter.
3. Reframing question. What would need to change so you would not enter the box.
4. My response: Well, if I had children or people depending on me, I could not enter.

Surprising conclusion! Aha! Then you do believe that there is a difference between a happiness box and the real world, namely your acceptance of the existence of other minds and the obligations those minds place on you.

That distinction was important to me, not only intellectually but in how I approached my life.

Hope this contributes to the conversation.

David