tommy. i do think you are missing his/her point.
ayn rand is not logical in offering any "should" or "should not" in regard to rational self interest. "self interest" can only be determined by self. how else could it be "self interest."
Desire is by nature subjective. How could it be anything else? If I desire something there is a reason I desire it. It has a value for me that I place above something I might have in its place.
Desire comes from the subject- the person- not the object- the thing desired. There is a REASON for desiring something. A personal, subjective reason. If I desire to practice my faith there is something I find of value in that. I value that over something else I could do.
Can Ayn Rand determine what every single persons desires "should be" in order to fit into her philosophy? Or does true self interest have to stem from the actual desire of the person choosing?
Desire is always rational. Meaning- there is a reason for it.