He would accurately point out its not an enzyme. However he would also incorrectly say that this a systme designed to produce high affinity, and therefore is not relevant
I would respond, the antibody system is just like evolution then, a system created by God to create new proteins.
I also remind him that the theory of intermediate stabilization predicts that antibodies, because the can adaptive ly bind things, can be catalysis. This is exactly what we find in Abzymes.
https://www.sciencedirect.com/topics/medicine-and-dentistry/catalytic-antibody
This demonstrates by theory and example that selective binding is functionally equivalent to catalysis. The reason we do not select for enzymes in experiments is because it is exteremely difficult for humans to select for catalytic activity at remotely the same scale we can select for binding.