If Proudhon argues that one ought not charge interest when lending, then Bastiat’s rebuttal is appropriate;

if Proudhon argues that one ought not have any special privilege which prevents others lending with less interest, and thereby allows one to charge interest when lending (without being undercut), then Bastiat’s rebuttal is irrelevant.

Richard Garner’s alternative argument is more relevant. Someone who is able to invest in the bank is less likely to need the loan than someone who is unable to invest in the bank. The approach might work for insurance…