So then it is my third question, which I admittedly reworded. Originally I meant to ask if it was a cultural distinction of about what is food, and that seems to be the answer then.
Essentially you seem to have said that what you consider to be ok to eat is what you have already ate or what has been accepted to be eaten by those around you.
I find that conclusion lacking, as it gives no room for future food discovery (unless you are ok with being passive and just eating whatever others tell you is ok to eat).
But back to your question.
> if it was shown in the future that “asparagus and trees” and even their separated fruit had bundles of nerves, conditional logic, feelings, intelligence, does that also exclude them from diets now?
If it is believed that “asparagus and trees” have the ability to feel joy, feel pain, feel compassion, live some definition of a fulfilling life, and that harvesting them effectively killed all of that. Then yes, I think it would certainly bring into question the morality of mass farming, killing, and eating them.
Of course, if it turns out that everything has this capability, from the smallest nanobes to the largest mammals, and we haven't worked out how to produce nutrients at scale, then maybe we just need to throw our hands up and say "whelp, survival of the fittest".