I suspect it is someone who is attracted to stupidity at the
extreme. Someone who is indifferent to intelligence could be either
non-sexually inclined, inclined for "normal" reasons, or inclined
to be sexually attracted to ignorant people. That would be
extremely unusual and ... uh stupid.
Another way to answer this question is to define an
anti-sapiosexual as someone who is not only unattracted by
intelligence, but threatened by it. This could be just someone who
has been traumatized and fearful. Someone just not capable of
forming any kind of sexual relationship.