If there are only two people involved then I think survival takes precedence and either man will dispense that as he sees fit for the situation. Will this washed up man kill me? How and when do I determine that? If I think the washed up man is dangerous, then what is my best solution?
All dangers aside I certainly would share a banana, water, stories, laughs, etc. with him, not because I assume he has natural rights that I must comply with, but because of the joy it would bring. I am not really concerned with his rights natural or not.
I would hope theories would not be involved in my thinking. Organizing a nation is one thing, the perils of two people on an island is another.
I have wondered about one man alone on planet Earth. In effect, that man in his mind owns the planet. Then a second man appears, immediately the first man’s ownership drops to half. They know nothing of rights at all. What would happen, would war break out??? If so should it be judged? Could either man walk away without looking over his shoulder? Would they discuss how they can live on the planet together? Who knows?