One reason against rationalist, though not a huge one, is that in philosophy it refers to an adherent of a particular theory of epistemology [...] it could lead to confusion (though obviously only among the relatively small number of people who have studied epistemology).

Since it's in Philosophy 101 (or so I assume), you don't need to study that much. The meaning of the term shifted over time, it's like appealing to the etymology of some normal word in the already pointless definition debate.