LISP is sort of it's own thing with it's homoiconicity (get into it now while you're young enough for it to take root better--you might like it,
Though in his case, as an R programmer, you might help break down resistance to experimentation more by reminding him that R is based on S and the Scheme dialect of Lisp.
Here we go again.
Got the hammer and tongs ready?
It's your language-based bias induced by the (mis)use of languages employing ITERATION which finds you (mis)representing and mis-characterizing the lisps in this way;
One can do much in the lisps via RECURSION which allows one to `recur' rather than reITERATE.
Of course one can iterate on both lists and vectors as well as exploit recursion on the -- singly linked -- lists available via the lisps.
That's one of the things I like about programming languages though--way easier to pick up new ones than natural languages, especially for me.
Though sometimes it's the programming paradigms a language will support, allow, and promote as per linguistic relativity which matters MORE -- cognitively, expressively -- than a specific language a newb can wrap his or her mind around.
To wit, to my mind the functional paradigm learned during the same developmental interval in a learner's life as `Algebra' can facilitate the learning of BOTH in a synergistic mutually-reinforcing way which can help the learner refrain from imbuing special superstitious reverence for the notation revered by the math weenies who favor their notation over those employed by programming languages which support the functional paradigm.